修复 UI 预览测试隔离

卸载 ExclusiveChildrenTabs 测试实例，避免后续 tab 查询命中残留 DOM。

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

@@ -286,7 +286,7 @@ describe('UI tree preview visibility', () => {
   it('uses a highlighted tab bar for exclusive child switching', () => {
     const parent = exclusiveNode('parent', [node('child-a'), node('child-b')]);
     const onSelectChild = vi.fn();
-    render(
+    const rendered = render(
       <ExclusiveChildrenTabs
         parent={parent}
         isChildVisible={(nodeId) => nodeId === 'child-a'}
@@ -306,6 +306,7 @@ describe('UI tree preview visibility', () => {
     ).toBe('false');
     fireEvent.click(screen.getByRole('tab', { name: 'child-b' }));
     expect(onSelectChild).toHaveBeenCalledWith('child-b');
+    rendered.unmount();
   });
 
   it('keeps exclusive tab pointer gestures out of the parent node', () => {