The reviewed PR stack is now merged into main, so an open draft PR #19 is
no longer proof that the reviewed code is what runs. The mandatory
release.exact-lineage-is-running check now requires the merged terminal
state instead: PR #19 closed with merged=true, base main, the existing
feature ref, and the exact reviewed head, plus a new merge-ancestry step
that proves the reviewed head is an ancestor of the pinned origin/main
via git merge-base --is-ancestor. An open PR, a PR closed without
merging, a mismatched head, or a head that is not a proven ancestor of
main still fails closed; an undecidable ancestry probe is NOT_RUN. The
recorded pre-merge base SHA is no longer compared against current main.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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