feat: workspace aliases, tab groups of split panes, native path picker (v2.1.0)

- /api/workspaces and `agenthub workspace(s)` / `--workspace` as aliases of
  /api/lanes and `agenthub lanes` / `--lane`; old names print one stderr note.
  REPL `help lanes|workspace|workspaces` resolves through the aliases.
- A workspace holds up to ten sessions (slots 0-9); every console tab is a
  group of 1-4 split panes (PaneGroups, agenthub.workspace.paneLayout);
  parseGroups keeps the stored active tab when an earlier one is dropped.
- Browse button beside path fields: POST /api/lanes/pick-path opens the OS
  picker on the server's desktop — loopback only and no forwarding header
  (EREMOTE), a display failure is ENODIALOG not a Cancel, the dialog is
  killed when the request closes, a folder field falls back to the in-app
  browser on any failure.
- Changes rail counts chip, image viewer (/git/raw), status bar session
  counts and per-day cost (`date=` on /api/pricing/cost).
- /agenthub-open and /agenthub-doctor run from the INSTALLED build
  (supersededBy), doctor offers fixes behind two confirmations; plugin-open
  treats a locked bootstrap as non-fatal.
- New-terminal shell waits for the first attach (issue #55).
- repo-onboarding / debug-live-issue skills removed.
- OpenAPI: pick-path, lane/date on /pricing/cost, tool on /run/history,
  /api/workspaces mount.

client/src/components/run/LaneConsolePane.tsx

@@ -5,7 +5,7 @@
  * whose button goes back to the workspace home, where a session starts with a
  * prompt (a pane has no run form; the tab bar's `+`, `ConsoleTabs.tsx`, starts
  * a bare CLI or a shell). No header of its own: the tab bar is the console's
- * header. The Workspace page keeps one per tab (slot 0–3) mounted, the
+ * header. The Workspace page keeps one per live session (slot 0–9) mounted, the
  * inactive ones hidden with CSS.
  *
  * The pane is bound to the lane it shows: switching `laneId` swaps it to the
@@ -97,7 +97,7 @@ export function LaneConsolePane({
   // arrives — the request must land after that. Only this lane's own tabs.
   useEffect(() => {
     if (!attachRequest || laneId === null) return;
-    if (!new RegExp(`^agenthub-lane-${laneId}(-[1-3])?$`).test(attachRequest.runId)) return;
+    if (!new RegExp(`^agenthub-lane-${laneId}(-[1-9])?$`).test(attachRequest.runId)) return;
     let live = true;
     autoAttachedForLane.current = laneId;
     api.run