✅(frontend) add vitest so the frontend can carry unit tests

Add vitest as a dev dependency, a test script that runs panda
codegen first, and a test-front job, so the frontend can carry
unit tests. One test covers normalizeRoomId, a plain function,
so no DOM library comes with it.

.github/workflows/ci.yml

@@ -196,6 +196,25 @@ jobs:
       - name: Check format
         run: cd src/frontend/ && npm run check
 
+  test-front:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@d23441a48e516b6c34aea4fa41551a30e30af803 # v6.1.0
+
+      - name: Install Node.js
+        uses: actions/setup-node@249970729cb0ef3589644e2896645e5dc5ba9c38 # v6.5.0
+        with:
+          node-version: "22"
+
+      - name: Install dependencies
+        run: cd src/frontend/ && npm ci --ignore-scripts
+
+      - name: Run tests
+        run: cd src/frontend/ && npm test
+
   lint-sdk:
     runs-on: ubuntu-latest
     permissions: