feat: add unit tests and CI configuration

.github/workflows/test.yml

@@ -0,0 +1,27 @@
+# * Runs unit tests on push/PR to main and staging.
+name: Test
+
+on:
+  push:
+    branches: [main, staging]
+  pull_request:
+    branches: [main, staging]
+
+jobs:
+  test:
+    name: unit-tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Run tests
+        run: npm test