## What changed
Add a public `codex_core::guardian_review` module exposing `GuardianAssessment`, the assessment parser and output schema, and the review session configuration builder for reuse by the Guardian extension.
Extract assessment handling and reviewer configuration into dedicated modules, preserving the existing parsing defaults, policy prompt, and read-only reviewer settings.
## Testing
Move the existing embedded-JSON, bare allow/deny, and output-schema tests alongside the assessment implementation.
GitOrigin-RevId: cb2aba3ccdb597e2876015e718e923d4f8f36802
