release-runbook-author

What this owns, and what it does not

This owns the single-service release runbook: the ordered phases one service walks from pre-flight to post-release, the pass criteria written at each phase, and the way each phase compares what it observes against a baseline. The failure mode it addresses is a release where the steps live in someone's head, so "is it healthy?" gets answered by whoever is awake.

The cross-team sequencing problem - several interdependent services, owned by several teams, that must change over in a dependency order inside one shared window - is a separate procedure, worked in references/cutover-sequence.md. The division is clean: that procedure decides which service goes when and who may say stop for the window; this runbook is what a single service runs inside the slot it was given. If your release touches one service, you need only the runbook.