Strengthen production governance: promotion approval, canary rollout, rollback, and monitoring

The Toulmin analysis says the SDK’s production story is directionally strong but incomplete because it does not yet define approval workflows, canary criteria, rollback triggers, or monitoring guidance. The architecture already supports versioned policy snapshots and rollback, but the operational controls around them need to be made concrete.

This ticket should move the SDK from “architecturally safe” to “operationally governed.”

Suggested scope

Add policy promotion workflow support with approval records.
Add canary rollout configuration and comparison metrics between old and new policy versions.
Add rollback triggers and a clear recovery path.
Add monitoring guidance for judge drift, reward-quality degradation, and learning pause behavior.

Acceptance criteria

The repo includes example governance workflows or docs for rollout and rollback.
The runtime can support canary comparison with persisted metrics.
The docs clearly separate capture, training, and promotion controls.

No files or tests are named. Start by tracing the existing versioned policy snapshots and rollback support in the SDK, then inspect how runtime promotion and metrics are handled. Done means documented approval, canary, rollback, monitoring, and separate capture, training, and promotion controls, with persisted canary comparison metrics.