add WebSocket ping to keep connections alive through CloudFlare

CloudFlare drops idle WebSocket connections after ~100 seconds.
Ping every 30 seconds to prevent this.

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

gateway/src/channels/websocket-handler.ts

@@ -312,6 +312,7 @@ export class WebSocketHandler {
 
       // Handle disconnection
       socket.on('close', async (code: number, reason: Buffer) => {
+        clearInterval(pingInterval);
         logger.info({ sessionId: authContext.sessionId, code, reason: reason?.toString() }, 'WebSocket disconnected');
 
         // Unregister from event system
@@ -334,6 +335,14 @@ export class WebSocketHandler {
       socket.on('error', (error: any) => {
         logger.error({ error, sessionId: authContext.sessionId }, 'WebSocket error');
       });
+
+      // Ping every 30 seconds to keep the connection alive through CloudFlare proxy.
+      // CloudFlare drops idle WebSocket connections after ~100 seconds.
+      const pingInterval = setInterval(() => {
+        if (socket.readyState === 1) { // OPEN
+          socket.ping();
+        }
+      }, 30000);
     } catch (error) {
       logger.error({ error }, 'Failed to initialize session');
       socket.close(1011, 'Internal server error');