fix: show empty work preview without invoking the Agent

tests/unit/use-work-preview.test.tsx

@@ -7,6 +7,26 @@ beforeEach(() => { vi.useFakeTimers(); ensure.mockReset(); });
 afterEach(() => vi.useRealTimers());
 
 describe('work preview request lifecycle', () => {
+  it('stops polling an empty project and checks again when the work tab is reopened', async () => {
+    ensure.mockResolvedValue({ status: 'empty' });
+    const onResult = vi.fn();
+    const { result, rerender } = renderHook(({ enabled }) => useWorkPreview({ projectId: 'p1', enabled, onResult }), {
+      initialProps: { enabled: true },
+    });
+    await act(async () => {});
+    await act(async () => vi.advanceTimersByTimeAsync(60_000));
+    expect(result.current.result).toEqual({ status: 'empty' });
+    expect(onResult).toHaveBeenCalledWith({ status: 'empty' });
+    expect(ensure).toHaveBeenCalledTimes(1);
+
+    await act(async () => rerender({ enabled: false }));
+    ensure.mockResolvedValue({ status: 'ready' });
+    await act(async () => rerender({ enabled: true }));
+    expect(result.current.result).toEqual({ status: 'ready' });
+    await act(async () => vi.advanceTimersByTimeAsync(60_000));
+    expect(ensure).toHaveBeenCalledTimes(2);
+  });
+
   it('resumes a manually opened work page and ignores the older startup response', async () => {
     let finish!: (value: unknown) => void;
     ensure.mockImplementationOnce(() => new Promise((resolve) => { finish = resolve; })).mockResolvedValue({ status: 'ready' });