ADR-010: Conventional Commits, and git hooks run by lefthook

Every commit subject is a Conventional Commit, type(scope): description, with ! or a BREAKING CHANGE: footer marking a breaking change. The type decides whether a commit reaching main cuts a release, and how large (ADR-013), and the release notes are built from the subjects, so a wrong type ships a wrong version. No hook checks a subject; a reviewer does.

lefthook runs the git hooks configured in lefthook.yml: the unit tests before a commit, and before a push task quality:verify and the docs build. They are recommended rather than required, because CI runs the same gates on every pull request and CI is what refuses a change; a hook only tells you sooner. Install them with lefthook install. Do not skip a hook. A new gate that needs no Mattermost goes into task quality:verify, which the pre-push hook runs and CI runs step by step; govulncheck alone runs in CI only (ADR-014).

Not chosen

• pre-commit, the Python framework: A Python toolchain to install for a Go project, with versions pinned in its own configuration.
• A commit-msg hook that validates subjects: It runs only where it is installed, so it cannot be relied on, and a reviewer reads the subject anyway.