Add pre-commit hook (format, lint, test) and format the repo
- .githooks/pre-commit runs `format:check`, `lint`, and `test`; commits
are blocked unless all pass. Enabled via core.hooksPath, wired by a
`prepare` npm script so `npm install` activates it on fresh clones.
- Ran `prettier --write .` across the repo so it's now Prettier-clean and
the hook's format:check passes going forward.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>