ci: add github actions workflow for lint, format, test, build

PR-3 of the modernization plan: every push to master and every pull
request now runs npm ci then lint, format:check, test, build sequentially
on node 20 / ubuntu. All four are required.

- .github/workflows/ci.yml: single job, single matrix entry, npm cache
  keyed off package-lock.json.
- package.json: new format:check script (prettier --check, same scope as
  format) so CI doesn't have to abuse --write. engines.node set to >=20
  to mirror the runner.
- CLAUDE.md: documents both the new script and the CI gate.

This is the safety net before the TypeScript rewrite of src/ lands.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: tkirda-bison

.github/workflows/ci.yml

@@ -0,0 +1,24 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+
+      - run: npm ci
+
+      - run: npm run lint
+      - run: npm run format:check
+      - run: npm test
+      - run: npm run build

CLAUDE.md

@@ -12,8 +12,13 @@ This is a single-file jQuery plugin (Ajax Autocomplete). The entire implementati
 - `npm run test:watch` — Vitest watch mode for local TDD.
 - `npm run lint` — ESLint (flat config in `eslint.config.mjs`) over `src/`, `test/`, and `scripts/build.mjs`.
 - `npm run format` — Prettier rewrite of `src/`, `test/`, and `scripts/build.mjs` (100-col, 4-space, ES5 trailing commas — config in `package.json`). Demo files under `scripts/` (`countries.js`, `demo.js`) are intentionally excluded.
+- `npm run format:check` — Prettier check-only, same scope. Used by CI; fails if anything would be rewritten.
 - `npm run build` — runs `scripts/build.mjs` (Node ESM, no bundler): copies `src/jquery.autocomplete.js` to `dist/jquery.autocomplete.js` while substituting the `%version%` placeholder with `package.json` `version`, minifies to `dist/jquery.autocomplete.min.js` via terser with a fresh banner, and syncs `devbridge-autocomplete.jquery.json` version. Run this before release/commit when source changes.
 
+## CI
+
+`.github/workflows/ci.yml` runs on every push to `master` and every pull request: `npm ci`, then `lint`, `format:check`, `test`, `build` — in that order, all required. Node 20 LTS, Ubuntu, single job. The `engines.node` field in `package.json` mirrors the runner version.
+
 ## Tests
 
 Vitest + jsdom, headless. Specs live in `test/autocomplete.test.js`. `test/setup.js` attaches a single jQuery instance to the jsdom `window` and `globalThis`, registers `jquery-mockjax` against it, silences mockjax's per-request console logging, then loads `src/jquery.autocomplete.js`. The plugin's UMD wrapper picks up `globalThis.jQuery` and registers `$.Autocomplete` plus `$.fn.autocomplete`/`$.fn.devbridgeAutocomplete` against that same instance.

package.json

@@ -13,10 +13,14 @@
   "scripts": {
     "build": "node scripts/build.mjs",
     "format": "prettier --write ./src ./test ./scripts/build.mjs",
+    "format:check": "prettier --check ./src ./test ./scripts/build.mjs",
     "lint": "eslint ./src ./test ./scripts/build.mjs",
     "test": "vitest run",
     "test:watch": "vitest"
   },
+  "engines": {
+    "node": ">=20"
+  },
   "repository": {
     "type": "git",
     "url": "git://github.com/devbridge/jQuery-Autocomplete.git"