- Deleted `ClientAdapter` implementation and associated fallback methods.
- Removed legacy executor logic from `codex`, `claude`, `gemini`, and `qwen` executors.
- Simplified `handlers` by eliminating `UnwrapError` handling and related dependencies.
- Cleaned up `model_registry` by removing logic associated with suspended clients.
- Updated `.gitignore` to ignore `.serena/` directory.
- Added model suspension with reason tracking for 401 (unauthorized) and 402/403 (payment-related) errors.
- Implemented resumption logic upon model quota recovery or auth state changes.
- Enhanced registry to manage suspended clients, including counts and observability data.
- Updated availability computation to exclude suspended clients, ensuring accurate client model tracking.
- Implemented `/v1/completions` endpoint mirroring OpenAI's completions API specification.
- Added conversion functions to translate between completions and chat completions formats.
- Introduced streaming and non-streaming response handling for completions requests.
- Updated `server.go` to register the new endpoint and include it in the API's metadata.
