Block pushes and commits to main with git hooks

pre-push rejects any push that would update refs/heads/main, however the
command is spelled; pre-commit and pre-merge-commit refuse commits while
main is checked out. npm install enables them via core.hooksPath. The
README documents the three layers of protection for main.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -3,6 +3,7 @@
 A tiny todo CLI that exists to try out [Claude Code](https://docs.claude.com/en/docs/claude-code) features.
 
 ```sh
+npm install   # once per clone: turns on the git hooks in .githooks/
 npm test
 npm start -- add "try Claude Code"
 npm start -- done 1
@@ -18,6 +19,12 @@ npm start -- ls
 | `.claude/skills/changelog/` | A custom skill — run `/changelog` |
 | `.claude/agents/test-writer.md` | A custom subagent — "use the test-writer agent to…" |
 
+### Protecting `main`
+Changes reach `main` only through a PR that a human merges. Three layers, strongest first:
+1. **Gitea branch protection** on `main` (set in the repo settings on code.westerkam.org): the only layer that can't be bypassed from a clone.
+2. **Git hooks** in `.githooks/` (enabled by `npm install`): `pre-push` rejects any push that would update `main`, however it's spelled; `pre-commit` / `pre-merge-commit` refuse commits while `main` is checked out. `--no-verify` skips them.
+3. **Claude Code deny rules** in `.claude/settings.json` for `git push … main`: a quick early stop, but they match command text, so they're easy to get around.
+
 ## Things to try
 
 - *"There's a bug in how ids are assigned after removing a todo — find it and fix it with a test."*