Google subscription OAuth fails: CodeAssist onboardUser returned no project id

Bug

Connecting the Google subscription provider fails after Google OAuth completes.

Environment

• Manifest self-hosted instance
• Manifest version: v6.23.0
• Provider: Google subscription (Gemini)
• Browser OAuth flow with callback URL pasted manually because the localhost callback is not reachable

Steps to reproduce

1. Open Providers → Subscriptions.
2. Click Connect for Google.
3. Sign in with Google and approve the OAuth request.
4. Copy the resulting callback URL from the browser and paste it into the Manifest form.
5. Click Connect.

Actual result

The connection is not created. The page shows:

Failed to exchange token. The URL may have expired. Try logging in again.

The page also reports:

CodeAssist onboardUser returned no project id.

The Google provider remains disconnected and still shows Connect.

Expected result

After successful OAuth, Manifest should create an active Google subscription connection and discover the available Gemini models.

Additional details

The Google account has Google Cloud projects, but the Manifest Google connection form provides no way to select or configure a project ID. The failure appears to happen during Google Code Assist onboarding after OAuth succeeds. Please either resolve the project ID automatically, provide a project-ID configuration option, or return the underlying eligibility/project requirement clearly instead of reporting an expired callback URL.