fix(shell): prevent duplicate websocket connects with synchronous lock

The shell connection hook relied on React state (isConnecting/isConnected) as the only guard for connect attempts. Because state updates are asynchronous, rapid connect triggers could race before isConnecting became true and create duplicate WebSocket instances.

This change adds a synchronous ref lock (connectingRef) that is checked immediately in connectToShell and connectWebSocket. connectToShell now sets connectingRef.current = true before invoking connectWebSocket so concurrent calls cannot pass between state updates.

connectWebSocket now:
- returns early when a connection is already locked
- sets connectingRef.current = true when creating a socket
- clears connectingRef.current alongside setIsConnecting(false) in onopen, onclose, onerror, and catch
- clears connectingRef.current when no WebSocket URL is available

disconnectFromShell also resets connectingRef to keep lock/state behavior consistent across manual disconnect flows.

src/components/shell/hooks/useShellConnection.ts

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useState } from 'react';
+import { useCallback, useEffect, useRef, useState } from 'react';
 import type { MutableRefObject } from 'react';
 import type { FitAddon } from '@xterm/addon-fit';
 import type { Terminal } from '@xterm/xterm';
@@ -50,6 +50,7 @@ export function useShellConnection({
 }: UseShellConnectionOptions): UseShellConnectionResult {
   const [isConnected, setIsConnected] = useState(false);
   const [isConnecting, setIsConnecting] = useState(false);
+  const connectingRef = useRef(false);
 
   const handleProcessCompletion = useCallback(
     (output: string) => {
@@ -101,23 +102,29 @@ export function useShellConnection({
     [handleProcessCompletion, setAuthUrl, terminalRef],
   );
 
-  const connectWebSocket = useCallback(() => {
+  const connectWebSocket = useCallback(
-    if (isConnecting || isConnected) {
+    (isConnectionLocked = false) => {
+      if ((connectingRef.current && !isConnectionLocked) || isConnecting || isConnected) {
         return;
       }
 
       try {
         const wsUrl = getShellWebSocketUrl();
         if (!wsUrl) {
+          connectingRef.current = false;
+          setIsConnecting(false);
           return;
         }
 
+        connectingRef.current = true;
+
         const socket = new WebSocket(wsUrl);
         wsRef.current = socket;
 
         socket.onopen = () => {
           setIsConnected(true);
           setIsConnecting(false);
+          connectingRef.current = false;
           setAuthUrl('');
 
           window.setTimeout(() => {
@@ -154,18 +161,22 @@ export function useShellConnection({
         socket.onclose = () => {
           setIsConnected(false);
           setIsConnecting(false);
+          connectingRef.current = false;
           clearTerminalScreen();
         };
 
         socket.onerror = () => {
           setIsConnected(false);
           setIsConnecting(false);
+          connectingRef.current = false;
         };
       } catch {
         setIsConnected(false);
         setIsConnecting(false);
+        connectingRef.current = false;
       }
-  }, [
+    },
+    [
       clearTerminalScreen,
       fitAddonRef,
       handleSocketMessage,
@@ -178,15 +189,17 @@ export function useShellConnection({
       setAuthUrl,
       terminalRef,
       wsRef,
-  ]);
+    ],
+  );
 
   const connectToShell = useCallback(() => {
-    if (!isInitialized || isConnected || isConnecting) {
+    if (!isInitialized || isConnected || isConnecting || connectingRef.current) {
       return;
     }
 
+    connectingRef.current = true;
     setIsConnecting(true);
-    connectWebSocket();
+    connectWebSocket(true);
   }, [connectWebSocket, isConnected, isConnecting, isInitialized]);
 
   const disconnectFromShell = useCallback(() => {
@@ -194,6 +207,7 @@ export function useShellConnection({
     clearTerminalScreen();
     setIsConnected(false);
     setIsConnecting(false);
+    connectingRef.current = false;
     setAuthUrl('');
   }, [clearTerminalScreen, closeSocket, setAuthUrl]);