Promote a revision to production

Make this already-built revision the live production revision without rebuilding. Pins the app's default production timeline to this revision (joining the timeline first if needed), so the default managed production host — and any custom domains assigned to the app's production timeline — route to it, and it runs with the production context's environment variables and databases.

This differs from attaching the default production alias via PUT /revisions/{revision}/domains: that only marks the revision as a production member and lets the newest member serve, whereas this pins this specific revision, so it serves even when it is older than another production revision. To undo, promote a different revision (re-pins) or remove the production override.

The revision must be built (status routed). Returns 204 No Content.