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/__tests__/LaneDiffView.test.tsx

@@ -502,3 +502,34 @@ describe("LaneDiffView — hunk review bar navigation", () => {
     expect(screen.getByTestId("lane-diff-view").className).not.toContain("max-h-[60vh]");
   });
 });
+
+describe("LaneDiffView — line comments", () => {
+  it("writes a comment on a new line and hands over `<path>:<line> — <text>`", () => {
+    const sent: string[] = [];
+    let delivered = false;
+    render(
+      <LaneDiffView
+        file={FILE}
+        layout="unified"
+        onComment={(text) => {
+          sent.push(text);
+          return delivered;
+        }}
+      />
+    );
+    fireEvent.click(screen.getByTestId("diff-comment-line-1"));
+    fireEvent.change(screen.getByRole("textbox"), { target: { value: "rename this" } });
+    fireEvent.submit(screen.getByTestId("diff-comment-box"));
+    expect(sent).toEqual(["server/lib/git-ops.js:1 — rename this"]);
+    // No pane took it: the box stays, with the reason.
+    expect(screen.getByRole("alert")).toBeInTheDocument();
+    delivered = true;
+    fireEvent.submit(screen.getByTestId("diff-comment-box"));
+    expect(screen.queryByTestId("diff-comment-box")).toBeNull();
+  });
+
+  it("offers no comment button without onComment", () => {
+    render(<LaneDiffView file={FILE} layout="unified" />);
+    expect(screen.queryByTestId("diff-comment-line-1")).toBeNull();
+  });
+});