Add pre-commit hook and CLAUDE.md

.husky/pre-commit

@@ -0,0 +1 @@
+npx lint-staged

CLAUDE.md

@@ -0,0 +1,40 @@
+# mock-openai
+
+## Before Every Commit
+
+Run these checks on all changed files before committing:
+
+```bash
+pnpm run format:check    # prettier
+pnpm run lint            # eslint
+pnpm run test            # vitest
+```
+
+If prettier or eslint fail, fix with:
+
+```bash
+npx prettier --write <files>
+npx eslint --fix <files>
+```
+
+A pre-commit hook (husky + lint-staged) runs prettier and eslint automatically
+on staged files, but always verify manually before pushing — CI checks the
+entire repo, not just staged files.
+
+## Project Structure
+
+- `src/` — TypeScript source (server, router, helpers, responses, types)
+- `src/__tests__/` — Vitest test suite
+- `docs/` — GitHub Pages website (static HTML)
+- `fixtures/` — Example fixture JSON files shipped with the package
+
+## Testing
+
+- Tests live in `src/__tests__/` and use Vitest
+- When adding features or fixing bugs, add or update tests
+- Run `pnpm test` before pushing
+
+## Commit Messages
+
+- Plain English, no conventional commit prefixes (no feat:, fix:, chore:, etc.)
+- No Co-Authored-By lines

package.json

@@ -36,7 +36,12 @@
     "test:exports": "publint && attw --pack .",
     "lint": "eslint .",
     "format:check": "prettier --check .",
-    "release": "pnpm build && changeset publish"
+    "release": "pnpm build && changeset publish",
+    "prepare": "husky"
+  },
+  "lint-staged": {
+    "*.{ts,mts,js,mjs,cjs,json,html,css,md}": "prettier --write",
+    "*.{ts,mts,js,mjs}": "eslint --fix"
   },
   "devDependencies": {
     "@arethetypeswrong/cli": "^0.17.3",
@@ -46,6 +51,8 @@
     "@eslint/js": "^9.30.0",
     "eslint": "^9.30.0",
     "eslint-config-prettier": "^10.1.5",
+    "husky": "^9.1.7",
+    "lint-staged": "^16.3.2",
     "prettier": "^3.6.2",
     "publint": "^0.3.12",
     "tsdown": "^0.12.5",