ci: add observational ESLint check (#550)

.github/workflows/test.yml

@@ -13,6 +13,26 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  lint:
+    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: Lint
+        run: yarn lint
+
   unit-tests:
     runs-on: ubuntu-latest
     timeout-minutes: 20