Move UI validation into separate github action

.github/workflows/build.yml

@@ -96,11 +96,6 @@ jobs:
         git add --intent-to-add .
         git diff --stat --exit-code
 
-    - name: Validate UI
-      # skip UI validation for pull requests if UI is unchanged
-      if: ${{ github.event_name != 'pull_request' || steps.cache-ui.outputs.cache-hit != 'true' }}
-      run: make ui-validate
-
     - name: Build UI
       # skip UI build for pull requests if UI is unchanged (UI was cached)
       # this means that the build version/time may be incorrect if the UI is

.github/workflows/frontend-lint.yml

@@ -0,0 +1,39 @@
+name: Lint (frontend)
+on:
+  push:
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+
+      - name: Install PNPM
+        uses: pnpm/action-setup@v4
+        with:
+          version: 9
+
+      - name: Cache node packages
+        uses: actions/cache@v4
+        env:
+          cache-name: cache-node_modules
+        with:
+          path: frontend/node_modules
+          key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('frontend/pnpm-lock.yaml') }}
+
+      - name: Install node packages
+        run: make pre-ui
+
+      - name: Validate UI
+        run: make ui-validate