🐛 Fix MCP plugin reconnect loop on duplicate connection (#11520)

The MCP server closes duplicate plugin connections with 1008 (policy
violation). The plugin treated every close as retryable: shouldReconnect
stayed true, scheduleReconnect re-armed, and each brief onopen reset the
backoff - looping at ~1s until the browser froze. Treat 1008 closes as
terminal and stay disconnected until the user reconnects explicitly.

mcp/packages/plugin/src/main.ts

@@ -255,6 +255,15 @@ function connectToMcpServer(baseUrl?: string, token?: string): void {
                 updateCurrentTask(null);
             }
             ws = null;
+            if (event.code === 1008) {
+                // Policy violation (e.g. duplicate connection for the same user
+                // token - another tab already holds the connection). Retrying
+                // would be refused again immediately, so stay disconnected
+                // until the user explicitly reconnects.
+                shouldReconnect = false;
+                cancelReconnect();
+                return;
+            }
             scheduleReconnect();
         };