Broken onboarding UX: First launch creates an empty unauthenticated profile, requiring a manual logout to trigger OAuth

[Kassaila]

Describe the bug

The onboarding flow for the agy CLI is completely broken for first-time users. Upon the very first launch, the CLI asks for a UI theme preference and then immediately drops the user into the TUI agent interface without initiating any authentication or OAuth flow.

Once inside, the agent is unusable (unauthenticated), and there are no clear instructions or in-app commands (like /login) to authenticate. The only way to actually trigger the Google OAuth login screen is to guess that you need to run a logout command first to destroy the broken, auto-generated empty profile.

Steps to reproduce

1. Install the antigravity CLI on a clean machine without pre-existing Google/gcloud credentials.
2. Run agy for the first time.
3. The CLI prompts to choose a theme color.
4. Select a theme. The CLI immediately opens the main TUI chat interface.
5. Try to send a message to the agent -> it fails due to a lack of credentials, but offers no way to log in.
6. (Workaround) Discover that you have to somehow trigger a logout sequence to finally see the actual Google OAuth prompt.

Expected behavior

On the first run, if no valid API keys or active Google OAuth tokens are detected, the CLI must explicitly prompt the user to authenticate before or during the initial setup, rather than silently creating a dead, unauthenticated session.

Environment

• OS: Linux (Ubuntu 22.04)
• Terminal: Bash