- Incremented `defaultClientVersion` and `defaultCodexUserAgent` to `0.144.1`.
- Replaced GPT-5.5 with GPT-5.6 Sol in model registry, updating metadata including context window length, reasoning levels, and description.
- Enhanced model metadata with adjusted parameters, reasoning format, and new effort levels.
- Bumped the `defaultClientVersion` and `defaultCodexUserAgent` to `0.144.0`.
- Replaced GPT-5.6 Sol with GPT-5.5 in model registry, adjusting metadata including context window length and reasoning levels.
- Updated `usage_helpers` to include `cache_write_tokens` logic for input token details.
- Registered new GPT-5.6 models (Sol, Terra, Luna) with detailed configurations, including increased context length and advanced reasoning levels.
- Updated client model configurations and metadata for GPT-5.6 Sol in `codex_client_models.json`.
- Relocated Codex client model JSON and related logic from `openai` package to `registry` for better modularity.
- Updated references to use `registry.GetCodexClientModelsJSON()` in loading logic.
- Extended test cases to cover additional field removals (`upgrade`, `availability_nux`).
