fix: prevent reconnection loop on concurrent connection close

- Don't reconnect when server closes old connection with code 4000
- Code 4000 means new connection was established, not an error
- Prevents infinite reconnection loop between old/new connections

Refs: terminal switching between 4000 error and connected

apps/web/src/components/terminal.tsx

@@ -133,7 +133,7 @@ export const TerminalComponent: React.FC<TerminalProps> = ({
         heartbeatCheckRef.current = null;
       }
       
-      if (event.code !== 1000) {
+      if (event.code !== 1000 && event.code !== 4000) {
         setError(`Connection closed (code: ${event.code})`);
 
         // Attempt reconnection
@@ -146,6 +146,10 @@ export const TerminalComponent: React.FC<TerminalProps> = ({
             }
           }, delay);
         }
+      } else if (event.code === 4000) {
+        // Server closed old connection for concurrent connection - don't reconnect
+        // The new connection is already established
+        console.log("Old WebSocket closed by server (new connection established)");
       }
     };