ci: Add test pipeline for Node 18/20/22

Run TypeScript build check and vitest on every push/PR across Node 18,
20, and 22.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: karlwaldman

.github/workflows/test.yml

@@ -0,0 +1,33 @@
+name: Test Node SDK
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    name: Test (Node ${{ matrix.node-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        node-version: ["18", "20", "22"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node-version }}
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: TypeScript build check
+        run: npm run build
+
+      - name: Run tests
+        run: npm test