feat: GCE forever agent with Cloud Run bridge support

- Add gce-startup.sh: self-contained VM startup (install, build, configure, run)
- Add start-forever.js: dual-process launcher for local development
- Add npm scripts: start:forever, start:bridge
- Bind A2A listener to 0.0.0.0 (was 127.0.0.1) for remote bridge access
- Pre-configure all headless settings to bypass interactive dialogs
- Use .env file + script pseudo-TTY for systemd service

packages/cli/src/external-listener.ts

@@ -393,7 +393,7 @@ export function startExternalListener(options?: {
       },
     );
 
-    server.listen(port, '127.0.0.1', () => {
+    server.listen(port, '0.0.0.0', () => {
       const address = server.address();
       const actualPort =
         typeof address === 'object' && address ? address.port : port;