test: introduce frontend unit testing foundation (#529)

.github/workflows/test.yml

@@ -0,0 +1,37 @@
+name: Frontend Tests
+
+on:
+  pull_request:
+    branches:
+      - v2
+
+permissions:
+  contents: read
+
+concurrency:
+  group: frontend-tests-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  unit-tests:
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+
+      - name: Setup Node
+        uses: actions/setup-node@v7
+        with:
+          node-version: '24'
+          cache: yarn
+          cache-dependency-path: yarn.lock
+
+      - name: Install dependencies
+        run: yarn --frozen-lockfile
+
+      - name: Typecheck
+        run: yarn typecheck
+
+      - name: Unit tests with coverage
+        run: yarn test:coverage