chore(ci): add lefthook git hooks manager

.lefthook/commit-msg/commit-msg-lint.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+# Commit message validation — called by lefthook commit-msg hook.
+# $1 is the path to the temporary commit message file.
+
+MSG=$(cat "$1")
+
+# Skip validation for merge commits
+if echo "$MSG" | grep -qE '^Merge '; then
+  exit 0
+fi
+
+# Enforce type(scope): summary format per CONTRIBUTING.md
+if ! echo "$MSG" | grep -qE '^(feat|fix|docs|chore|refactor|test)(\([a-z-]+\))?: .+'; then
+  echo "ERROR: commit message must match: type(scope): summary" >&2
+  echo "  Types: feat, fix, docs, chore, refactor, test" >&2
+  exit 1
+fi

README.md

@@ -13,13 +13,32 @@ A starter template for new GitHub repositories.
 | `.github/workflows/ci.yml` | Generic GitHub Actions CI workflow (the `npm ci` and `npm test` steps skip when no `package.json` exists) |
 | `AGENTS.md` | Instructions for AI coding agents |
 | `CLAUDE.md` | Imports `AGENTS.md` so Claude Code picks up the same instructions |
+| `lefthook.yml` | Git hooks manager config (pre-commit + commit-msg) |
 
 ## How to use
 
 1. Go to the [template repository](https://github.com/new?template_owner=iap&template_name=.github).
 2. Create a new repository from this template.
 3. Customize the files for your project.
 
+## Git Hooks (Lefthook)
+
+This template includes `lefthook.yml` for git hook management.
+
+```bash
+# Install lefthook (via mise or your package manager)
+mise use lefthook
+
+# Install hooks into .git/hooks/
+lefthook install
+```
+
+Hooks configured:
+- **pre-commit**: runs `npm run lint` if package.json exists (skips merge/rebase)
+- **commit-msg**: enforces `type(scope): summary` commit message format via `.lefthook/commit-msg/commit-msg-lint.sh`
+
+Scripts live under `.lefthook/<hook-name>/`. Override with `git commit --no-verify` when needed.
+
 ## License
 
 This project is licensed under the MIT License — see the [LICENSE](LICENSE) file for details.

lefthook.yml

@@ -0,0 +1,22 @@
+# Lefthook — git hooks manager
+# Docs: https://lefthook.dev
+#
+# Install: lefthook install
+# Validate: lefthook validate
+
+pre-commit:
+  commands:
+    lint:
+      run: |
+        # Run project lint if available
+        if [ -f package.json ] && command -v npm >/dev/null 2>&1; then
+          npm run lint
+        fi
+      skip:
+        - merge
+        - rebase
+
+commit-msg:
+  scripts:
+    "commit-msg-lint.sh":
+      runner: bash