test: allow the long-history warm-switch regression to finish

Scope a 15-second budget to the 161-message switching scenario while retaining all render-count, DOM reuse, draft, attachment, and scroll assertions. The full App suite, typecheck, and lint pass.

src/renderer/src/App.test.tsx

@@ -4732,7 +4732,7 @@ describe("App", () => {
     historyRenderProbes.pane.mockClear();
     fireEvent.change(screen.getByLabelText('向 GoodBuddy 提问'), { target: { value: 'Warm cached draft' } });
     expect(historyRenderProbes.pane).toHaveBeenCalledTimes(0);
-  });
+  }, 15_000);
 
   it("requires an accessible confirmation before permanently deleting a conversation", async () => {
     render(<App />);