add test-cicd code

code/sample-nodejs-app/index.js

@@ -0,0 +1,23 @@
+const express = require('express');
+const app = express();
+const port = process.env.PORT || 3000;
+
+app.get('/', (req, res) => {
+  res.json({
+    message: 'Hello World from Antigravity!',
+    status: 'success',
+    timestamp: new Date().toISOString()
+  });
+});
+
+app.get('/health', (req, res) => {
+  res.status(200).send('OK');
+});
+
+if (require.main === module) {
+  app.listen(port, () => {
+    console.log(`Server is running on port ${port}`);
+  });
+}
+
+module.exports = app;