Agent Skills: ship-tag

Cut, tag and publish versioned releases and build CHANGELOG.md in Keep a Changelog 1.1.0 format: release/vX.Y.Z branch, PR retarget, version bump, annotated tag on the reviewed merge commit, reproducible tar.gz published as an Azure Artifacts Universal Package, read back and checksum-verified. USE WHEN release, cut a release, version tag, tag vX.Y.Z, release branch, publish package, tar.gz, universal package, changelog, CHANGELOG.md, keep a changelog, release notes, yanked. NOT FOR PR labels or opening PRs (use ship).