## Summary
- Promote `image_generation` from under-development to stable
- Enable image generation by default in the feature registry
- Update feature coverage for the new launch-state expectation
- Add the missing image-generation auth fixture field in a tool registry
test
## Testing
- `just fmt`
- `cargo test -p codex-features`
- `cargo test -p codex-tools` currently fails:
`test_full_toolset_specs_for_gpt5_codex_unified_exec_web_search` needs
its expected default tool list updated for `image_generation`
85203d8872