测试：模型状态文案改走底部 toast 后改用异步查询

- `conversationModelSelect.test.tsx` 两处同步 `screen.getByText('…')` 改为 `await screen.findByText(…)`：状态文案现在渲染在 portal 的 toast 里（发布 → 宿主 re-render 一次），同步查询在慢机/并行下会竞态（CI 上就是这样红的）
- 本地：`npx vitest run tests/conversationModelSelect.test.tsx` 29 passed；`appSurface + chatDialogFrameLayout` 225 passed / 9 skipped

Refs #600, PR #607

apps/ai-game-creator-shell/tests/conversationModelSelect.test.tsx

@@ -526,7 +526,10 @@ test('pre-send validation falls back when the selected model is disabled', async
   await act(async () => {
     await expect(ref.current?.ensureUsable()).resolves.toBe(true);
   });
-  expect(screen.getByText('所选模型已停用，已切换为默认模型')).not.toBeNull();
+  // 状态文案现在走组件自带的底部 toast（portal 到 body）：等它出现，别用同步查询。
+  expect(
+    await screen.findByText('所选模型已停用，已切换为默认模型'),
+  ).not.toBeNull();
   expect(savedModelId).toBe('quality');
   expect(invoke).toHaveBeenCalledWith('select_game_creator_model', {
     modelId: 'quality',
@@ -552,7 +555,7 @@ test('follows the new server default when the saved selection was the default',
   await waitFor(() => expect(savedModelId).toBe('fast'));
   expect(savedModelIsDefault).toBe(true);
   expect(
-    screen.getByText('默认模型已更新，已切换为新的默认模型'),
+    await screen.findByText('默认模型已更新，已切换为新的默认模型'),
   ).not.toBeNull();
   expect(invoke).toHaveBeenCalledWith('select_game_creator_model', {
     modelId: 'fast',