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__/SessionResumeButton.test.tsx

@@ -1,10 +1,10 @@
 /**
  * @file SessionResumeButton.test.tsx
- * @description The transcript page's explicit Resume: it shows only for a
+ * @description The transcript page's explicit Resume and Fork: it shows only for a
  * Claude session inside a workspace, a live session offers its pane instead,
  * and a resume asks first (it re-reads the whole transcript), then starts in
  * the first free pane slot and opens that pane — or refuses when all four are
- * busy.
+ * busy; a Fork asks too and starts a new session id beside a live original.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -114,6 +114,28 @@ describe("SessionResumeButton", () => {
     expect(screen.getByTestId("where").textContent).toBe("/workspace?lane=3&run=agenthub-lane-3");
   });
 
+  it("forks into a free pane after asking, even while the original has a live pane", async () => {
+    runs = [
+      {
+        id: "agenthub-lane-3",
+        laneId: 3,
+        slot: 0,
+        status: "running",
+        sessionId: "s-1",
+      } as RunHandle,
+    ];
+    const user = userEvent.setup();
+    renderButton({ id: "s-1", cwd: "/r", tool: "claude" });
+    await user.click(await screen.findByRole("button", { name: "Fork" }));
+    expect(screen.getByRole("dialog")).toHaveTextContent("NEW session");
+    await user.click(screen.getByRole("button", { name: "Fork session" }));
+    expect(api.lanes.action).toHaveBeenCalledWith(3, "start", {
+      slot: 1,
+      resumeSessionId: "s-1",
+      forkSession: true,
+    });
+  });
+
   it("offers no Resume for a session started in a subfolder, but opens its live pane", async () => {
     const { unmount } = renderButton({ id: "s-9", cwd: "/r/lib", tool: "claude" });
     await waitFor(() => expect(api.run.list).toHaveBeenCalled());