What task are you trying to do?

Add a CI check that fails PRs whose title does not follow Conventional Commits (feat:, fix:, refactor:, docs:, chore:, ci:…), matching the updated AGENTS.md convention.

Context

Split out of #54 (P3 polish). Originally drafted as [Feature]/[Bug] title lint; revised after realizing that convention only covered two of the real PR types (refactor, docs, chore, ci, upstream-sync all slipped through). Conventional Commits covers them natively, aligns with commit-message lint (#69), and survives squash merges where the PR title becomes the commit message.

amannn/action-semantic-pull-request is the standard tool for this.

Issue titles are unaffected — they continue to use [Feature]/[Bug] via the existing issue templates at .github/ISSUE_TEMPLATE/*.yml.

What would a good result look like?

• PRs with non-conforming titles show a failing check.
• Action is SHA-pinned (matches D5 policy in [Feature] Harden CI as a real merge gate for dev #54).
• Check is not required in the ruleset (advisory is fine for P3).
• Upstream-sync PRs (squash merge from graft) produce conformant titles by virtue of using chore: or feat: in the squashed commit.

Audience

Maintainers.