chore: enforce pre-PR validation (aggregate scripts, git hooks, PR checklist) (#1061)

* chore: enforce pre-PR validation with aggregate scripts, git hooks, and PR checklist

Add tooling to help contributors run the same checks as CI before
submitting a pull request, reducing avoidable format/lint/build failures.

- Add aggregate npm scripts:
  - `npm run check` runs format-check + lint + build + test (mirrors CI)
  - `npm run fix` runs format + lint:fix + build
- Add husky + lint-staged git hooks (installed via `npm install`):
  - pre-commit formats and lints staged files
  - pre-push rebuilds dist/ and runs the test suite
- Add a checklist item to the PR template prompting contributors to run
  `npm run check` locally
- Document the aggregate scripts and hooks in docs/contributors.md

dist/ is intentionally not auto-committed by CI to avoid pwn-request
security risks; the existing `Check dist/` workflow continues to verify it.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

package.json

@@ -13,10 +13,22 @@
     "format-check": "prettier --no-error-on-unmatched-pattern --config ./.prettierrc.js --check \"**/*.{ts,yml,yaml}\"",
     "lint": "eslint --config ./.eslintrc.js \"**/*.ts\"",
     "lint:fix": "eslint --config ./.eslintrc.js \"**/*.ts\" --fix",
+    "check": "npm run format-check && npm run lint && npm run build && npm test",
+    "fix": "npm run format && npm run lint:fix && npm run build",
+    "prepare": "husky install",
     "prerelease": "npm run-script build",
     "release": "git add -f dist/setup/index.js dist/cleanup/index.js",
     "test": "jest"
   },
+  "lint-staged": {
+    "*.ts": [
+      "prettier --no-error-on-unmatched-pattern --config ./.prettierrc.js --write",
+      "eslint --config ./.eslintrc.js --fix"
+    ],
+    "*.{yml,yaml}": [
+      "prettier --no-error-on-unmatched-pattern --config ./.prettierrc.js --write"
+    ]
+  },
   "repository": {
     "type": "git",
     "url": "git+https://github.com/actions/setup-java.git"
@@ -50,8 +62,10 @@
     "eslint-config-prettier": "^10.1.8",
     "eslint-plugin-jest": "^29.0.1",
     "eslint-plugin-node": "^11.1.0",
+    "husky": "^9.1.7",
     "jest": "^30.4.2",
     "jest-circus": "^30.4.2",
+    "lint-staged": "^17.0.8",
     "prettier": "^3.6.2",
     "ts-jest": "^29.4.11",
     "typescript": "^5.3.3"