Treat PR readiness as an infrastructure trigger when previews run

When GitHub Actions provisions previews on ready_for_review, marking a pull request ready can create Supabase branches before the application reaches Railway deployment. Inspect that event's workflow before treating readiness as a metadata-only action, especially when deployment is excluded. Cancelling the run is asynchronous and does not roll back completed provisioning: verify the terminal result and individual steps, then inventory partial resources rather than claiming nothing changed. This applies to workflows with early infrastructure steps; it does not imply that every ready transition deploys, or that cancellation proves cleanup.

Applies when: PR review events automatically provision database or application previews. Keywords: GitHub Actions ready_for_review Supabase Railway preview cancellation provisioning cleanup