Confirm a production deploy actually landed and is healthy. Verifies the latest Vercel Production deployment is READY and matches the current `main` commit, runs HTTP canary checks against travel.matthewcarr.dev, confirms migrations applied, and checks for a post-deploy Sentry error spike. Use after merging to `main`, or when a human asks "is prod healthy?" / "did the deploy go out?" / "smoke test production". Read-only against prod by default.