Migrate core render util to use xterm.js as part of the rendering loop. (#19044)

packages/cli/src/test-utils/AppRig.test.tsx

@@ -5,6 +5,7 @@
  */
 
 import { describe, it, afterEach, expect } from 'vitest';
+import { act } from 'react';
 import { AppRig } from './AppRig.js';
 import path from 'node:path';
 import { fileURLToPath } from 'node:url';
@@ -68,7 +69,11 @@ describe('AppRig', () => {
     );
     rig = new AppRig({ fakeResponsesPath });
     await rig.initialize();
-    rig.render();
+    await act(async () => {
+      rig!.render();
+      // Allow async initializations (like banners) to settle within the act boundary
+      await new Promise((resolve) => setTimeout(resolve, 0));
+    });
 
     // Wait for initial render
     await rig.waitForIdle();