feat(ui): a Claude-Desktop-style home for every workspace

/workspace?lane=<id> opens on the workspace's home (WorkspaceHome): a prompt
box whose Start opens a new session in the first free pane slot, Recents (a
live session attaches its pane, any other opens its transcript, nothing
resumes), and Instructions / Memory / Context / Folder. Instructions live in
lanes.instructions, extra folders and uploaded files in the new lane_sources
table (copies under <data dir>/workspace-context/<lane id>/); spawnRun reads
them from the lane's rows and hands Claude --add-dir + an appended system
prompt file, Codex --add-dir + developer_instructions. Memory is read-only.

Every dashboard pane carries AGENTHUB_RUN_ID; hooks forward it and the run
records which session the pane holds (a Claude pane follows /clear and
/resume but not a nested claude -p), so the sidebar and notifications open
the right pane (&run=). Settings loses its Projects group; Worktrees now
decides which worktrees Add folder suggests.

client/src/hooks/__tests__/useNotifications.test.ts

@@ -145,6 +145,34 @@ describe("useNotifications", () => {
     vi.restoreAllMocks();
   });
 
+  it("links a notification to the pane that holds the session, in any slot", async () => {
+    fetchMock.mockImplementation(async (url: string) => ({
+      ok: true,
+      json: async () =>
+        url === "/api/push/send"
+          ? { ok: true, native: true, pushed: 1 }
+          : url === "/api/run"
+            ? {
+                items: [
+                  { id: "agenthub-lane-4-2", laneId: 4, status: "running", sessionId: "s-7" },
+                ],
+              }
+            : { lanes: [], counts: {} },
+    }));
+    enable();
+    renderHook(() => useNotifications());
+    eventBus.publish({
+      type: "new_event",
+      timestamp: new Date().toISOString(),
+      data: { event_type: "Stop", summary: "Done", session_id: "s-7" } as DashboardEvent,
+    });
+    await vi.waitFor(() => expect(sentTitles()).toHaveLength(1));
+    const push = fetchMock.mock.calls.find((c) => c[0] === "/api/push/send")!;
+    expect(JSON.parse((push[1] as RequestInit).body as string).url).toBe(
+      "/workspace?lane=4&run=agenthub-lane-4-2"
+    );
+  });
+
   it("stays silent while notifications are disabled", async () => {
     renderHook(() => useNotifications());