Add CSS build check to CI

- Add Node.js setup and npm ci to CI workflow
- Verify compiled.css is up-to-date by rebuilding and checking for diffs
- Add package-lock.json to lock dependency versions
- Remove package-lock.json from .gitignore

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: 2 people

.github/workflows/ci.yml

@@ -24,6 +24,17 @@ jobs:
         uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
         with:
           fetch-depth: 1
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+      - name: Install npm dependencies
+        run: npm ci
+      - name: Check CSS is up-to-date
+        run: |
+          npm run build-css
+          git diff --exit-code stylesheets/compiled.css || (echo "Error: compiled.css is out of date. Run 'npm run build-css' and commit the changes." && exit 1)
       - name: Setup Ruby
         uses: ruby/setup-ruby@a6e6f86333f0a2523ece813039b8b4be04560854 # v1.190.0
         with:

.gitignore

@@ -9,6 +9,5 @@ vendor
 bin
 .jekyll*
 node_modules/
-package-lock.json
 _figma/
 _svg-backup/