feat: enhance request logs and proxy response handling

- Updated request logs panel to include detailed previews for both proxy request and response bodies.
- Implemented logging of response bodies in Codex upstream provider, allowing for better debugging and tracking of responses.
- Enhanced parsing logic in Codex to provide more descriptive lifecycle labels for thinking events, improving clarity in event streams.
- Added tests to ensure proper handling of proxy responses and lifecycle events, including capturing passthrough responses and verifying correct event ordering.
- Improved request log detail retrieval to include response body previews, ensuring comprehensive logging for requests.