- Add CODEOWNERS so PRs to main require owner review (closes the gap
where two collaborators could approve each other's changes).
- Gate the release job behind a 'release' environment, so signing
secrets are only unlocked after manual approval.
- Stop ignoring the whole .github directory; this had been silently
swallowing labeler.yml and workflows/labeler.yml, which are now tracked.
Paired with a tag ruleset (created out-of-band) that restricts creation
of v* tags to admins, this prevents a write collaborator from pushing a
tag to trigger a signed release build.
Jason