Babysit a PR

Keep an open PR moving toward merge by reacting to three streams as each arrives: review comments (handed to ce-resolve-pr-feedback), CI failures (handed to ce-debug), and branch-currency items the snapshot flags.

Outcome: the PR is left at a truthfully reported terminal, looks-ready, blocked, or out-of-budget state under the run's posture. Done: Step 3 (stop conditions) reached a true stop and the Step 4 report is written. Settled ≠ merged.

What each tick looks at and every change it makes come from the bundled pr-snapshot output — never by prose, events you notice, or a coordinator's say-so (readiness also applies the review judgment in references/settle.md, which reads live state this output does not model). Read references/tick.md before the first snapshot; references/envelope.md states the full boundaries.

Posture (one value per run)

• target — only the named PR; stop at looks-ready; never merges; offer stack-wide once if a confirmed managed stack needs work.
• stack-ready — once a layer has zero actionable backlog (CI may still run), advance to the next open non-draft upstack layer needing work; lower layers stay probed and the lowest that re-opens pulls the walk back; never merges.
• stack-land — as stack-ready, and selecting it is land authorization: once the bottom-most open layer is settled, gh stack merge it + gh stack sync.

One PR named → target (ask once if a confirmed multi-layer stack exists); asked to carry the whole stack → stack-ready; asked to land it → stack-land. mode:pipeline never asks. Restate posture per transition.

Non-negotiable boundaries