Updates the default configuration and documentation to prioritize the local codex proxy over public cloud endpoints.

- **Config**: Changes default `AI_REVIEW_API_URL` to `http://localhost:8088/v1/chat/completions`.
- **Models**: Updates default `MODEL` and `TRIAGE_MODEL` to `gpt-5.5` and `gpt-5.4-mini` respectively to align with codex naming conventions.
- **LLM**: Refines thinking mode logic to send hint parameters (`enable_thinking`, `thinking_budget`) to OpenAI-compatible gateways while maintaining compatibility with proxies that ignore these fields.
- **Documentation**: Updates `README.md` with detailed instructions for codex proxy deployment, including model resolution rules and GitLab CI variable configuration.
- **Timeouts**: Increases default `AI_REVIEW_DEEP_TIMEOUT` to 600 seconds in the documentation.