Store visual baselines as text assets

.github/workflows/css.yml

@@ -0,0 +1,67 @@
+name: CSS & Visual Regression
+
+on:
+  pull_request:
+    paths:
+      - "css/**"
+      - "docs/**"
+      - "tests/visual/**"
+      - "package-lock.json"
+      - "package.json"
+      - "playwright.config.ts"
+      - "tailwind.config.cjs"
+      - ".github/workflows/css.yml"
+  push:
+    branches:
+      - main
+    paths:
+      - "css/**"
+      - "docs/**"
+      - "tests/visual/**"
+      - "package-lock.json"
+      - "package.json"
+      - "playwright.config.ts"
+      - "tailwind.config.cjs"
+      - ".github/workflows/css.yml"
+
+jobs:
+  css:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Check CSS build artifacts are committed
+        run: npm run check:css
+
+      - name: Install Playwright browsers
+        run: npx playwright install --with-deps chromium
+
+      - name: Run visual regression tests
+        id: visual
+        run: npm run test:visual
+        continue-on-error: true
+
+      - name: Upload Playwright artifacts
+        if: steps.visual.outcome == 'failure'
+        uses: actions/upload-artifact@v4
+        with:
+          name: playwright-visual-diffs
+          path: |
+            playwright-report
+            test-results
+          if-no-files-found: ignore
+
+      - name: Fail if visual regressions detected
+        if: steps.visual.outcome == 'failure'
+        run: exit 1