test(ci): separate mobile menu checks from a11y suite

.github/workflows/test-mobile-menu.yml

@@ -0,0 +1,61 @@
+name: Mobile Menu Tests
+
+on:
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: mobile-menu-${{ github.head_ref || github.ref_name }}
+  cancel-in-progress: true
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  mobile-menu:
+    runs-on: ubuntu-latest
+    env:
+      HUGO_VERSION: 0.156.0
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          submodules: recursive
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: "1.26"
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: "24"
+          cache: npm
+
+      - name: Setup Hugo
+        run: |
+          wget -O ${{ runner.temp }}/hugo.deb https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_extended_${HUGO_VERSION}_linux-amd64.deb \
+          && sudo dpkg -i ${{ runner.temp }}/hugo.deb
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Install Playwright Chromium
+        run: npx playwright install chromium
+
+      - name: Build site
+        run: npm run build
+
+      - name: Run mobile menu tests
+        run: npm run test:mobile-menu
+
+      - name: Upload report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: mobile-menu-report
+          path: playwright-report/
+          retention-days: 14