QA: Authentication — CrewAI (Crews)

• Navigate to /demos/auth. The page mounts authenticated by default so the initial /info handshake succeeds without crashing the route.
• Verify the auth banner (data-testid="auth-banner") shows data-authenticated="true" and the "Sign out" button is visible.
• Send a message; verify the agent responds normally (no error banner).
• Click "Sign out"; verify the banner flips to data-authenticated="false" and the "Sign in" button is visible.
• Send a new message; verify the error banner (data-testid="auth-demo-error") appears with a 401 message. The ChatErrorBoundary should keep the rest of the page rendered (no white screen) — boundary fallback (data-testid="auth-demo-chat-boundary") may appear inside the chat container.
• Click "Sign in"; verify the banner flips back to authenticated, the error banner clears, and the chat is usable again without a page reload.