feat(pm): report the closing-keyword contradiction on the squash-commit surface (H23) (#11117)

Every closing-keyword reader in this repo is handed a PR body: H7 and H21 in
check-half-states.mjs, and the blocking gate check-partof-closing-keyword.mjs.
GitHub's parser also acts on commit messages landing on the default branch, and
this repo squash-merges, so each merged PR writes one such message that nothing
read.

H23 is a REPORT-ONLY patrol row over that surface. It reuses the existing
extractors at a new `markdown: false` surface option, because a commit message
is not markdown: quoting a keyword does not neutralise it there, so the finding
sentence prescribes rewording and never the body-surface remedy. The row states
its own coverage numbers in the summary line, and the bounded window is read
over REST because the patrol runner checks out shallow.

Measured over 1,546 first-parent messages on main (pinned window
2026-08-11T00:00Z to 2026-08-22T18:00Z): 270 keyword bindings across 234
messages, 6 carrying the contradiction, all 6 assembled by squash from a branch
that mixed the two trailer spellings.

Card: #10942

Co-authored-by: Claude <noreply@anthropic.com>

Author: claude[bot]