XY-855: Add independent fresh-context review orchestrator

[yvette-carlisle]

Summary

• Add structured independent fresh-context review checkpoints for loop-mode internal review.
• Persist accepted/rejected review findings in runtime state and private evidence.
• Update prompts, specs, and tests for clean, findings, rejected feedback, repair handoff, and non-converging escalation.

Verification

• cargo make fmt
• cargo make lint-fix
• cargo make test