feat: workspaces own their sessions; desktop parity; sidebar and settings cleanup

Workspace sessions (docs/plans/desktop-parity, phases 1-5 and 7):
- sessions.lane_id: a workspace lists only the sessions its panes held,
  stamped by bindRunSession (first writer wins, nested `claude -p`
  excluded); GET /api/sessions?lane=&archived=
- session row state dot, double-click rename, archive (sessions.archived_at,
  hides only); the activity bar's duplicate Sessions tab removed
- Fork beside Resume (--fork-session, Claude only), Ctrl/Cmd+click a live
  session opens it in a second pane, a diff line's comment is pasted into
  the workspace's last-focused pane (lib/panePaste.ts)

dashboard_runs stability:
- a pane's previous run is archived as <pane>@<started_at> instead of being
  overwritten by INSERT OR REPLACE
- a run is flagged abandoned only once its tmux session is gone, at boot and
  on the run-heal beat (panes outlive a server restart)

UI:
- sidebar: no footer, language or theme block; small collapse button in the
  brand corner; version + update check in the connection details modal, a
  status-bar dot while a release is out; language in Settings -> General
- one Switch component for every switch, the themed Checkbox for every
  checkbox (no native checkboxes)

Also: AI Tools catalog trimmed to 10 built-ins (custom-file prompt modes
tested through fixtures), and the workspace plans under docs/plans/ (the
multi-user server plan lives in the AgentHub-Server repo).

client/src/i18n/locales/en/lanes.json

@@ -88,6 +88,11 @@
   "changes.expandFile": "Expand {{path}}",
   "changes.fileGone": "That file no longer has changes in this range.",
   "changes.fileTruncated": "Diff cut short — open the file in an editor for the rest.",
+  "changes.commentLine": "Comment on line {{n}} — pasted into this workspace's pane",
+  "changes.commentOn": "Comment on {{at}} — pasted into the pane you used last; nothing is sent until you press Enter there",
+  "changes.commentSend": "Paste into pane",
+  "changes.commentCancel": "Cancel",
+  "changes.commentNoPane": "No pane of this workspace is open — open its session first",
   "changes.layout.split": "Side-by-side",
   "changes.layout.unified": "Unified",
   "changes.loading": "Reading the working copy…",
@@ -325,16 +330,17 @@
   "pane.close": "Stop this pane's session",
   "panel.files": "Files",
   "panel.changes": "Changes",
-  "panel.sessions": "Sessions",
-  "sessions.empty": "No sessions in this workspace yet",
   "sessions.resume": "Resume",
-  "sessions.open": "Open",
   "resume.openPane": "Open pane",
   "resume.hint": "Resume this session in a workspace pane — re-reads its whole transcript into context",
   "resume.title": "Resume this session?",
   "resume.body": "Resuming re-reads the session's whole transcript into the model's context, so its next turns pay for all of it again. It opens in the first free pane of {{workspace}}. To only read it, stay on this page.",
   "resume.confirm": "Resume session",
-  "sessions.search": "Filter sessions…",
+  "resume.fork": "Fork",
+  "resume.forkHint": "Continue from here as a NEW session — the original stays as it is",
+  "resume.forkTitle": "Fork this session?",
+  "resume.forkBody": "A fork re-reads the session's whole transcript into a NEW session (its own id), so its turns pay for all of it again; the original is left untouched. It opens in the first free pane of {{workspace}}.",
+  "resume.forkConfirm": "Fork session",
   "tree.title": "Workspaces",
   "tree.search": "Search workspaces and sessions",
   "tree.toolFilter": "Filter by tool",
@@ -342,6 +348,12 @@
   "tree.newSession": "New session",
   "tree.noSessions": "No sessions yet",
   "tree.transcriptHint": "No live pane — opens the transcript",
+  "tree.splitHint": "Live pane — Ctrl/Cmd+click opens it in a second pane",
+  "tree.renameSession": "Rename session",
+  "tree.archiveSession": "Archive — hide from this workspace (deletes nothing)",
+  "tree.archived_one": "{{count}} archived session",
+  "tree.archived_other": "{{count}} archived sessions",
+  "tree.unarchive": "Unarchive",
   "home.breadcrumb": "Workspaces",
   "home.repoRoot": "Repository root",
   "home.mainBranch": "Main worktree's branch",