- Implemented xAI OAuth2 integration with PKCE (Proof Key for Code Exchange) support. - Added logic for token exchange, refresh, and persistent storage in JSON format. - Created `xai` package with helpers for OAuth discovery, API token handling, and URL building. - Introduced `XAIExecutor` for integrating xAI credentials into runtime HTTP requests. - Added unit tests to validate OAuth flow, token persistence, and endpoint validation.