ci: enforce the commit format CLAUDE.md said was enforced

CLAUDE.md has claimed since the file was written that commitlint gates
the commit format in CI and that semantic-release runs off it. There was
no commitlint config, no workflow running one, and nothing invoking
.releaserc.yml — so the first thing every contributor and every agent
reads about this repo was false in two places.

scripts/commit-check.sh is the smaller honest answer: the grammar is one
regex, and commitlint would mean a Node dependency tree at the root of a
Go repo to run it. It is a commit-msg hook locally and a CI step over
every commit in a push, and its type list is .releaserc.yml's so the
check and the release rules cannot drift.

The semantic-release half is recorded as configured-but-not-wired rather
than implied to run.

.pi/skills/yellowjacket-dev/SKILL.md

@@ -128,6 +128,11 @@ first four are lefthook hooks, so skipping them locally only defers the
 failure; the typecheck is a hook too but only CI runs it over the test
 tree, which is where it has actually broken.
 
+The **message** is gated too: `make commit-check` (a `commit-msg` hook,
+and a CI step over every commit in a push) rejects a subject that is not
+`type(scope): subject`, is over 72 chars, or ends with a period. A
+`--no-verify` commit skips it locally and meets it in CI.
+
 Two things about the e2e tier that are not obvious until they bite.
 **The 36 specs share one backend process in file order**, so a spec
 that leaves the app somewhere passes alone and fails the suite — leave