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/components/lanes/LaneChangesPanel.tsx

@@ -29,6 +29,10 @@
  * file is conflicted) and **Abort merge** (two clicks, `confirm: true`), and
  * conflicted files get their own group with Keep mine / Take theirs / Mark
  * resolved instead of stage — staging one blind would mark it resolved.
+ *
+ * A diff line's number opens a comment box (LaneDiffView `onComment`); the
+ * comment is pasted, as `<path>:<line> — <text>`, into the workspace's pane
+ * focused last (`lib/panePaste.ts`) and sent only when the user presses Enter.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -56,6 +60,7 @@ import {
   UnfoldVertical,
 } from "lucide-react";
 import { api } from "../../lib/api";
+import { pasteToLane } from "../../lib/panePaste";
 import { LaneDiffView, LaneFileView, type DiffLayout, type LaneDiffChange } from "./LaneDiffView";
 import { LaneConflictView } from "./LaneConflictView";
 import { MarkdownPreview, isMarkdown } from "../MarkdownPreview";
@@ -436,6 +441,8 @@ export function LaneChangesPanel({
   // One read of the working copy, shared by the header and every write below:
   // a stage, a discard or a commit changes the counts the header shows.
   const [git, refreshGit] = useLaneGitFacts(laneId);
+  // A diff line's comment goes into this workspace's pane, as a paste.
+  const comment = useCallback((text: string) => pasteToLane(laneId, text), [laneId]);
   // Bumped by Refresh and by a git bar action: a pull or a switch moves
   // history and the tree too, not just the diff `load` re-reads.
   const [reread, setReread] = useState(0);
@@ -1558,6 +1565,7 @@ export function LaneChangesPanel({
                     layout={layout}
                     fill
                     hunkActions={whole ? undefined : hunkActions(current)}
+                    onComment={comment}
                   />
                 ) : null}
               </div>
@@ -1637,7 +1645,12 @@ export function LaneChangesPanel({
                       )}
                     </div>
                     {!shut && (
-                      <LaneDiffView file={f} layout={layout} hunkActions={hunkActions(f)} />
+                      <LaneDiffView
+                        file={f}
+                        layout={layout}
+                        hunkActions={hunkActions(f)}
+                        onComment={comment}
+                      />
                     )}
                   </div>
                 );