facts.test.sh: greenfield fixtures for all-zeros and empty event.before,
the bare root establishing labeled=no, and the D2 pin (an unresolvable
MERGE_SHA exits 128 and never reports base_ver=(none) — the test that
|| true would fail). release-chain.test.sh: chain() gains optional
repo/stub args; a -dev root commit is a green NOTICE ceremony=no, a bare
unlabeled root still refuses. Plus changelog.d/134.md.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The flip's mechanical half (#117): the 26 entries under '## Unreleased'
move verbatim to changelog.d/<issue>.md, the heading is deleted, the
directory gains its marker README (#112 D1) and this PR's own fragment
(112.md), CHANGELOG.md's preamble describes fragments, and labeler.yml
maps changelog.d/** into scope:release-flow.
