- Add 'antigravity' as new auth choice in onboard and configure wizards
- Implement Google Antigravity OAuth flow using loginAntigravity from pi-ai
- Update writeOAuthCredentials to accept any OAuthProvider (not just 'anthropic')
- Add schema sanitization for Google Cloud Code Assist API to fix tool call errors
- Default model set to google-antigravity/claude-opus-4-5 after successful auth
The schema sanitization removes unsupported JSON Schema keywords (patternProperties,
const, anyOf, etc.) that Google's Cloud Code Assist API doesn't understand.
