feat(workspace): VS Code-style split panes, edge-to-edge session view

The console splits into up to four panes: a binary split tree of tmux
slots (client/src/lib/paneLayout.ts) drawn by PaneGrid.tsx, every pane an
absolutely placed sibling keyed by slot so splitting, swapping, resizing
or closing never remounts a live terminal. Ctrl/Cmd+click on a tab, a +
item or a sidebar session row opens it beside the focused pane (router
state, never the URL); a pane header drags onto another pane's edge to
split there or onto its middle to swap, picks another live session,
splits right/down (a not-shown session or a new terminal), or closes the
pane only. Dividers drag or take arrow keys. ?run= is the focused pane:
every layout change goes through change(), which pushes the URL with
focusOnly instead of an effect watching the focus (that ping-ponged with
open requests). The layout is kept per workspace in localStorage.

Only the focused pane's terminal takes the keyboard when it appears, and
the keyboard follows a focus change. A pane closes when its terminal
reports the exit; the run list prunes only a remembered layout on a
workspace's first read and a just-opened slot that never got listed, so
one empty read cannot wipe a split. A run ending on the home or a replay
closes its pane without leaving the page.

The session view now fills the page edge to edge: no page padding, the
tab bar and the right panel's activity bar one h-10 strip, and the tab
bar, pane headers and right panel on the sidebar/status bar colour
(surface-1) around terminals on the page colour.

docs/LANES.md

@@ -391,7 +391,7 @@ The dashboard web UI merges workspaces and runs into a single **Workspace** page
 
 - **No page header.** The page title and the four counters (`lanes`, `running`, `needs you`, `dead`) are gone: the sidebar's workspace list shows every workspace with its own status dot, and the status bar at the bottom of every page counts running and need-you workspaces. `GET /api/lanes` still returns `counts` for other callers.
 - **The sidebar's workspace list picks the workspace** — on every page, below the nav (`client/src/components/WorkspaceTree.tsx`), shaped like Claude Desktop's project list: every workspace on ONE level (no repo grouping, no worktree rows), in your stored order. A row (`WorkspaceRow.tsx`) is a chevron, a status dot (green = active, pulsing while running; amber row = needs you; red = dead or error; grey = idle), the title or folder name and the tool's icon, with `+` (open it for a new session) and `⋯` on hover. Clicking the name opens `/workspace?lane=<id>` and expands the row: the URL is the selection, so a notification link, F5 and the back button all land on the same workspace, and a bare `/workspace` reopens the last one shown (`agenthub.workspace.selected`) or the first. The header has a **tool filter** (shown once workspaces of two tools exist; kept in `agenthub.sidebar.projects` → `tool`, a stored tool no workspace has filters nothing), search and `+` (Add workspace). Search matches workspace names and paths — such a workspace keeps all its sessions — and session names: a workspace whose name does not match still shows when one of its sessions does, with only the matching sessions under it (every list stays mounted, hidden, to load and count). In the collapsed rail the list is a single icon that opens the sidebar.
-- **A workspace's sessions** — the chevron expands the row to the sessions the workspace OWNS and has not archived (`WorkspaceSessionList.tsx`: `GET /api/sessions?lane=<id>&archived=0`, the newest 20, re-read when the workspace's status or session moves; which rows are expanded is kept in `agenthub.sidebar.projects` → `expanded`). A workspace owns a session its pane held — `bindRunSession` stamps `sessions.lane_id` from the pane's run, first writer wins, a nested `claude -p` excluded — and lists nothing else: a `claude` typed into a terminal in the same folder, or history from before the workspace existed, belongs to no workspace and is found on the Sessions page. Sessions older than this ownership column are not guessed: only those `dashboard_runs` still named were backfilled. A session started by a tool with no hooks (Codex without its hooks, any catalog tool) is never stamped. A row's dot is the session's state (`sessionDot`: amber waiting for you, red failed, green a live pane, hollow at rest); double-click renames it (`PATCH {name}`), and its hover button **archives** it (`PATCH {archived: true}` — hidden from the workspace, nothing deleted; the home lists the archived ones folded with **Unarchive**). A filled dot marks a session that still has a live pane (a `GET /api/run` handle carrying its session id — every pane the dashboard starts carries `AGENTHUB_RUN_ID=<its tmux name>`, the hook handler forwards it as `run_id`, and `bindRunSession` in `server/routes/hooks.js` records the hook's session on that run: the first session always, afterwards — for a Claude pane — only a `SessionStart` that is not a fresh `startup` (`/clear`, `/resume`), so a `claude -p` the agent runs inside the pane never takes it over; the rule is Claude-only, and a Codex or Antigravity pane follows every new session): clicking it opens `/workspace?lane=<id>&run=<runId>`, which ATTACHES pane 0 to that tmux session (`attachRequest` on `LaneConsolePane`) — it starts nothing and resumes nothing. The session opens on its own tab (the tab of its tmux slot). Any other session opens in its workspace the way Claude Desktop opens an old one: `/workspace?lane=<id>&session=<id>` shows its conversation, read-only (`SessionReplay.tsx`, the console hidden — never unmounted — behind it), with a prompt box under it. Opening it resumes nothing; **sending** a message resumes it (`POST /api/lanes/:id/start {slot, resumeSessionId, prompt}` in the first free pane slot, on the tool the session ran on) and opens that pane — a resume re-reads the whole transcript into context, so it waits for that explicit send. The session's analysis page (`/sessions/<id>`: agents, events, cost, transcript) is the **Analyst** button in the session view's right panel, beside Files and Changes (disabled while the pane's run has reported no session yet).
+- **A workspace's sessions** — the chevron expands the row to the sessions the workspace OWNS and has not archived (`WorkspaceSessionList.tsx`: `GET /api/sessions?lane=<id>&archived=0`, the newest 20, re-read when the workspace's status or session moves; which rows are expanded is kept in `agenthub.sidebar.projects` → `expanded`). A workspace owns a session its pane held — `bindRunSession` stamps `sessions.lane_id` from the pane's run, first writer wins, a nested `claude -p` excluded — and lists nothing else: a `claude` typed into a terminal in the same folder, or history from before the workspace existed, belongs to no workspace and is found on the Sessions page. Sessions older than this ownership column are not guessed: only those `dashboard_runs` still named were backfilled. A session started by a tool with no hooks (Codex without its hooks, any catalog tool) is never stamped. A row's dot is the session's state (`sessionDot`: amber waiting for you, red failed, green a live pane, hollow at rest); double-click renames it (`PATCH {name}`), and its hover button **archives** it (`PATCH {archived: true}` — hidden from the workspace, nothing deleted; the home lists the archived ones folded with **Unarchive**). A filled dot marks a session that still has a live pane (a `GET /api/run` handle carrying its session id — every pane the dashboard starts carries `AGENTHUB_RUN_ID=<its tmux name>`, the hook handler forwards it as `run_id`, and `bindRunSession` in `server/routes/hooks.js` records the hook's session on that run: the first session always, afterwards — for a Claude pane — only a `SessionStart` that is not a fresh `startup` (`/clear`, `/resume`), so a `claude -p` the agent runs inside the pane never takes it over; the rule is Claude-only, and a Codex or Antigravity pane follows every new session): clicking it opens `/workspace?lane=<id>&run=<runId>`, which ATTACHES to that tmux session (`attachRequest` on `LaneConsolePane`) — it starts nothing and resumes nothing. The session opens on its own tab (the tab of its tmux slot): in the pane already showing it (focused), else in the focused pane; **Ctrl/Cmd+click** opens it in a split beside the focused pane (see **Split panes** below). Any other session opens in its workspace the way Claude Desktop opens an old one: `/workspace?lane=<id>&session=<id>` shows its conversation, read-only (`SessionReplay.tsx`, the console hidden — never unmounted — behind it), with a prompt box under it. Opening it resumes nothing; **sending** a message resumes it (`POST /api/lanes/:id/start {slot, resumeSessionId, prompt}` in the first free pane slot, on the tool the session ran on) and opens that pane — a resume re-reads the whole transcript into context, so it waits for that explicit send. The session's analysis page (`/sessions/<id>`: agents, events, cost, transcript) is the **Analyst** button in the session view's right panel, beside Files and Changes (disabled while the pane's run has reported no session yet).
 - **Row menu** — right-click a row, or its `⋯` button: Start/Stop (slot 0), Rename, the Model (AI Router) select, Create/update readme file (Claude only), New workspace here…, Copy path, Reset worktree… (managed only) and Delete workspace…, each the call the rest of the UI already makes. Delete is record-only exactly as before (see "Removing a workspace").
 - **The workspace home** — `/workspace?lane=<id>` opens on the workspace's home (`client/src/components/lanes/WorkspaceHome.tsx`), shaped like a Claude Desktop project page: the name (rename from its `⋯` menu, which is the sidebar row menu) with the repository it belongs to under it (root, the main worktree's branch, the worktree count, from `GET /api/projects` — the facts Settings → Projects used to show), a prompt box — the one place a session starts WITH a prompt (a pane has no run form; the session view's tab bar `+` only starts a bare CLI or a shell) — whose fields run in order **AI** (the session's own tool: every installed, enabled one, the workspace's by default), **AI Router** (Native or a saved profile; Native alone, disabled, for a tool that cannot use one), **Model** (the tool's own list, or on a router that router's models), **Permission** (Claude's permission mode; Codex's sandbox and approval; a catalog tool's per-session bypass switch) and **Effort** (Claude and Codex), and whose **Start** opens a NEW session in the first pane slot with no live run (0–3, `POST /api/lanes/:id/start {slot}`; all four busy is refused) and then shows it, and **Recents** — the workspace's own sessions (`?lane=<id>`) with their cost and time, a live one opening its pane and any other its conversation (`&session=`), exactly like the sidebar. The transcript page (`/sessions/<id>`) of a Claude session started in a workspace's own folder carries an explicit **Resume** (`client/src/components/lanes/SessionResumeButton.tsx`, the one place that resumes) and beside it **Fork**, which resumes the history into a NEW session id (`{forkSession: true}` → `--fork-session`, the original untouched, offered even while the original has a live pane): it warns that a resume re-reads the whole transcript into context, re-reads the live panes, then starts it in the workspace's first free pane (`POST /api/lanes/:id/start {slot, resumeSessionId}`) and opens it. A session from a SUBFOLDER gets no Resume — the pane starts in the workspace's folder and Claude finds a session by the folder it ran in — and a session that still has a live pane shows **Open pane** instead. On the right sit the workspace's own context: **Instructions** (appended to every new session's system prompt), **Memory** (read-only: the folder's CLAUDE.md / AGENTS.md family and Claude's auto memory), **Context** (uploaded files, ≤ 10 MB each, stored by AgentHub) and **Folder** (the workspace's own folder plus extra ones, with the repo's untracked worktrees suggested). Only Claude and Codex panes can take them (`--add-dir`, `--append-system-prompt-file=` / `-c developer_instructions=`); for any other tool the page says so and its panes start without them. See `docs/API.md` → Workspace context. The home HIDES the session view with CSS — the console never unmounts behind it.
 - **A session in its own worktree** — Claude Desktop's worktree toggle: the row under the home's prompt box has a **Local / New worktree** select (Claude workspaces in a git repo). Claude Code itself makes a worktree only when started with `--worktree` or when asked mid-session — and a worktree it enters mid-session is invisible to AgentHub, which reads a session's folder once, at its start, and the new session's pane runs `claude --worktree=<name>`, so CLAUDE CODE makes `<repo>/.claude/worktrees/<name>` on branch `worktree-<name>`, copies `.worktreeinclude`, runs your `WorktreeCreate` hook, and on exit removes a worktree with no changes (or asks). AgentHub adds `/.claude/worktrees/` to the repo's `info/exclude` (Claude does not, and the main repo would list it). The session stays this workspace's own — listed with a branch icon and the worktree's name — and the session view's Changes panel works in ITS worktree (every git route with `?session=`, resolved from the session row: owned by the workspace, registered by `git worktree list`; `ENOWORKTREE` otherwise, never the main folder). Resume and Fork start in that worktree. **Archive** of a worktree session with no live pane asks first and removes the worktree like Claude Desktop — `git worktree remove` without force (git refuses unsaved work, and then nothing is archived) and `git branch -d` (unmerged work keeps its branch); a lock held by a live process refuses, a stale one is cleared. The workspace's own folder is never removed.
@@ -402,9 +402,11 @@ The dashboard web UI merges workspaces and runs into a single **Workspace** page
 - **Renaming a workspace** — double-click its sidebar row (or Rename in the row menu) to edit in place. **Enter** saves via `PATCH /api/lanes/:id` with `{title}`, **Escape** and clicking away both cancel, and saving an empty name clears the title, which puts the folder name back in its place. Renaming is display-only — a managed workspace's branch name was slugified from its title once, at creation.
 - **No header row** — the session view has no header of its own: the console's tab bar is it (status, the workspace's name and the back arrow are gone — the name is on the sidebar row and the home). Only a workspace with an installed pipeline template shows its time-on-stage, pipeline picker and feature picker above the console; there are no stage chips — the declared stage and the `auto: <stage>` detection both render in the PipelineMap. The **Tools** menu (mcp sync / sync-base check / create-update readme, hidden when the workspace declares no runtime profile) sits at the right end of the tab bar. The detail block (the workspace card, the PipelineMap, the proof gallery) is always shown, and Delete lives in the sidebar row menu. Tools sits on the workspace rather than in Settings because every one of its actions runs against one workspace's `cwd`. **Create/update readme file** (Claude workspaces only — Codex has no slash commands) starts the workspace's terminal run with `/sg-all:sg-md-writing` as its first message, so the workspace opens already writing/refreshing its `CLAUDE.md`/`AGENTS.md` set; it needs the `sg-all` plugin installed in Claude Code, and without it the session just reports an unknown command.
 - **Detail panel** — the selected workspace's declared stage, its inferred stage when detection leads, a full-width pipeline map, and a legend naming all five node states plus the dashed-amber inferred treatment Hidden while no pipeline template is installed (see "Pipeline stages and the five node states").
-- **Terminal** — a real interactive terminal (xterm.js) displaying the tmux session's PTY output, with full support for interactive commands, editors, and pagers. A live run keeps its rendered history and scroll position when scrolling. It grabs the keyboard the moment it appears, so typing goes into the pane without clicking it first. A pane has **no run form of its own**: a session with a prompt starts from the workspace home's prompt box. There is no **New run** button: when the active tab's process ends (a double Ctrl+C out of `claude`, `exit`, a crash) the next open tab is shown, or the home when none is left; a tab with nothing to show offers **New session**, which opens the home too.
+- **Terminal** — a real interactive terminal (xterm.js) displaying the tmux session's PTY output, with full support for interactive commands, editors, and pagers. A live run keeps its rendered history and scroll position when scrolling. It grabs the keyboard the moment it appears, so typing goes into the pane without clicking it first. A pane has **no run form of its own**: a session with a prompt starts from the workspace home's prompt box. There is no **New run** button: when a pane's process ends (a double Ctrl+C out of `claude`, `exit`, a crash) its pane closes; the last one shows the next open tab, or the home when none is left. A pane with nothing to show offers **New session**, which opens the home too.
 - **Clipboard in a pane** — the workspace's tmux session is started with the graphical session's own `DISPLAY`/`WAYLAND_DISPLAY`/`XAUTHORITY`/`XDG_RUNTIME_DIR` (read from `systemctl --user show-environment`, this process's own values winning; `server/lib/desktop-env.js`). The dashboard normally runs as a systemd *user* service, which has none of them, so a pane it started had no clipboard at all and `claude` answered "no image found in clipboard" on every image paste while the same CLI pasted fine in a terminal. Only those four names are forwarded, and only into panes this dashboard spawns — an already-running pane keeps the environment it was started with, so it needs a restart to gain one.
-- **Tabs** — the session view's console is a tab bar (`client/src/components/run/ConsoleTabs.tsx`), one tab per live tmux session of the workspace — at most four, its slots 0–3: slot 0 is the workspace's `agenthub-lane-<id>` (its `run_id`), slots 1–3 are `agenthub-lane-<id>-<slot>`. A tab shows its AI tool's icon and name (or **Terminal**); the active tab is the URL's `?run=`, so the Changes panel and Analyst follow it. Every tab with a live run stays mounted and the inactive ones are hidden with CSS, so switching tabs never drops a terminal. A tab's **×** stops its session (`DELETE /api/run/<runId>`) and moves to the next tab, or the home. The **+** menu opens a new tab in the first free slot: **New terminal** (your own default shell in the workspace folder — `POST /api/lanes/:id/start {slot, shell: true}`, recorded as tool `shell`; it is not an agent, so the workspace's `run_id`/`status` are left alone), each installed, enabled AI tool (started bare, on its default model, no prompt), and **Agent settings…** (Settings → Agents). With four tabs open **+** is disabled. EVERY tab is bound to the sidebar's selection. A tab has no header of its own (no title, no **Active runs** list, no **New run**): other sessions are opened from the sidebar or the home's Recents. The 1/2/4 split layout and its `agenthub.workspace.splitView` key are gone.
+- **Tabs** — the session view's console is a tab bar (`client/src/components/run/ConsoleTabs.tsx`), one tab per live tmux session of the workspace — at most four, its slots 0–3: slot 0 is the workspace's `agenthub-lane-<id>` (its `run_id`), slots 1–3 are `agenthub-lane-<id>-<slot>`. A tab shows its AI tool's icon and name (or **Terminal**); the active tab is the focused pane's, which is the URL's `?run=`, so the Changes panel and Analyst follow it, and a tab another pane shows carries a grey underline. A click shows a tab in the focused pane (or focuses the pane already showing it), **Ctrl/Cmd+click** — on a tab or on a `+` item — opens it in a split, and a tab drags onto the panes. Every tab with a live run stays mounted and those no pane shows are hidden with CSS, so switching tabs never drops a terminal. A tab's **×** stops its session (`DELETE /api/run/<runId>`) and closes its pane; with no pane left it moves to the next tab, or the home. The **+** menu opens a new tab in the first free slot: **New terminal** (your own default shell in the workspace folder — `POST /api/lanes/:id/start {slot, shell: true}`, recorded as tool `shell`; it is not an agent, so the workspace's `run_id`/`status` are left alone), each installed, enabled AI tool (started bare, on its default model, no prompt), and **Agent settings…** (Settings → Agents). With four tabs open **+** is disabled. EVERY tab is bound to the sidebar's selection. A tab has no header of its own (no title, no **Active runs** list, no **New run**): other sessions are opened from the sidebar or the home's Recents. (The old fixed 1/2/4 split layout and its `agenthub.workspace.splitView` key are gone; **Split panes** replaces them.)
+
+- **Split panes** — the console splits like VS Code (`client/src/components/run/PaneGrid.tsx`, model in `client/src/lib/paneLayout.ts`): a binary tree of splits, each side by side or stacked at a ratio, whose leaves are the workspace's slots — at most four panes, one per live session, a session never shown twice. **Ctrl/Cmd+click** a tab, a `+` item or a sidebar session row opens it to the right of the focused pane (the intent rides on the navigation's state, never in the URL); with more than one pane each gets a slim header: **drag** it (or a tab) onto another pane — its edge splits there, its middle swaps the two —, its **▾** shows another live session in it (swapping with the pane that showed it), **Split right / Split down** puts a not-shown session or a **New terminal** beside it, and **×** closes the pane only (its session stays a tab). Dividers drag (or move by arrow keys) between 10% and 90%. Clicking in (or tabbing into) a pane focuses it, `?run=` follows — so the right panel, Analyst and the sidebar read the focused session — and the keyboard goes with it: only the focused pane's terminal takes it when it appears. A pane closes when its terminal reports that its session ended (exited, closed from another browser); the run list itself only prunes a remembered layout on a workspace's first read, and a pane opened here whose session never got listed — one empty read, which the server returns on any tmux error, never wipes a split. A session ending while the home or a replay is shown only closes its pane; the URL stays. The layout is a viewer preference kept per workspace in `localStorage` (`agenthub.workspace.paneLayout`), never on the server. Every pane is an absolutely placed sibling keyed by its slot, so splitting, swapping or resizing never re-parents — and so never remounts — a live terminal; the session view itself fills the page edge to edge, its tab bar and the right panel's activity bar one header strip.
 - **Workspace grid** — one card per workspace, 1 column, 2 at `md`, 3 at `xl`. Each card carries the workspace id, liveness dot and status, title, declared stage and time-on-stage, the `auto:` chip when detection leads, the kind and CI tags, the working-copy facts from `GET /api/lanes/:id/git`, and the action row. The needs-you message (`needs_action`) is on the workspace list tile only — the detail card no longer repeats it as a banner.
 
 Run history is per workspace, queryable via `GET /api/run/history?laneId=<n>`.