- Add registry generation tracking and a Codex catalog revision accessor to provide stable cache keys.
- Cache parsed model templates and rendered spawn-agent markdown, and reuse them across requests when revision/generation are unchanged.
- Invalidate/recompute caches when model registrations or catalog content change, and separate rewrite handling for spawn tool descriptions vs. message encryption stripping.
Closes: #4967
Load codex_client_models.json like models.json with validation, revisioned
handler reloads, CI bake, and Home-aware updater gates so list IDs still
come from Home while templates can refresh on the edge.
- 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`).
