- Add `gpt-6-astra` model specifications and capabilities to registry models.
- Update Codex client models configuration and instructions for `gpt-6-astra`.
- Bump default Codex client version and user-agent to `0.153.3` in model fetcher tool.
- Add missing model schema fields including `multi_agent_reasoning_effort`, `requires_sandboxed_review`, `persistent_instructions`, `guardian_v2`, and `confirmation_policies`.
- Raise GPT 5.6 Sol/Terra/Luna `context_length` values to `921000` in `internal/registry/models/models.json`.
- Update matching Codex client model settings to `context_window: 272000` and `max_context_window: 921000` in `internal/registry/models/codex_client_models.json`.
- 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`).
