Make review and release readiness policy-aware in Assist mode

[StatPan]

Goal

Make review and release readiness useful as neutral GitHub inspection in Assist mode and strict policy validation only where a repository opts in.

Scope

• Consume the operation-mode/delivery-policy resolver in review queue and release readiness.
• Use branch-protection/provider facts as the neutral baseline.
• Apply closure-link, approval, and label requirements only from an explicit managed policy.
• Record policy provenance and finding class in JSON and human output.

Non-goals

• Do not change ticket start or finish mutation behavior.
• Do not weaken explicitly configured release policy.
• Do not add a separate release workflow.

Acceptance Criteria

• A conventional external PR is inspectable without an unconditional Gira policy failure in Assist mode.
• Explicit managed policy retains closure-link and approval enforcement with clear provenance.
• Release readiness inherits the selected policy behavior predictably.

Doctor Impact

No doctor rule change is expected; report consumers must distinguish provider facts from managed-policy checks.

Expected Delivery

• One focused PR after Add explicit operation-mode and delivery-policy configuration #936 supplies the shared policy contract.

Verification

• Focused review/release tests and go test ./... before PR.