feat: Add GitHub Actions CI (lint + tests)

.github/README.md

@@ -0,0 +1,18 @@
+# GitHub Actions
+
+## CI workflow
+
+[`workflows/ci.yml`](workflows/ci.yml) runs on pull requests and pushes to `master`: install dependencies, `npm run lint`, and `npm test`.
+
+It uses `npm ci` for both the repo root and `src/server`, matching the current lockfile-based setup on `master`.
+
+## Require CI before merging (branch protection)
+
+After this workflow is on the default branch:
+
+1. In the GitHub repo, go to **Settings** → **Branches**.
+2. Add or edit a rule for `master`.
+3. Enable **Require status checks to pass before merging**.
+4. Under **Status checks that are required**, select **CI / ci** (or the job name shown after the first run).
+
+This blocks merging PRs until lint and tests pass.

.github/workflows/ci.yml

@@ -0,0 +1,25 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [master]
+  push:
+    branches: [master]
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+      - name: Install root deps
+        run: npm ci --legacy-peer-deps
+      - name: Install server deps
+        run: npm --prefix src/server ci
+      - name: Lint
+        run: npm run lint
+      - name: Test
+        run: npm test

package.json

@@ -30,7 +30,7 @@
     "build": "npm --prefix admin run build && NODE_ENV=production webpack --config build/webpack.config.js",
     "serve": "cd src/server && NODE_ENV=development node app.js",
     "lint": "eslint .",
-    "test": "node --test \"test/**/*.test.js\""
+    "test": "node --test"
   },
   "husky": {
     "hooks": {