[FrankenPHP] Check for XDEBUG_SESSION cookie before connecting to debugger

Only connect to the Xdebug client when the XDEBUG_SESSION cookie is set.
This replicates the behavior in non-worker environments where the debugger
only activates when explicitly enabled through the debug toolbar.

Author: Karsten Nilsen

src/frankenphp-symfony/src/Runner.php

@@ -33,8 +33,8 @@ public function run(): int
         $server['APP_RUNTIME_MODE'] = 'web=1&worker=1';
 
         $handler = function () use ($server, &$sfRequest, &$sfResponse, $xdebugConnectToClient): void {
-            // Connect to the Xdebug client if it's available
-            if ($xdebugConnectToClient) {
+            // Connect to the Xdebug client if it's available and the XDEBUG_SESSION cookie is set
+            if ($xdebugConnectToClient && isset($_COOKIE['XDEBUG_SESSION'])) {
                 xdebug_connect_to_client();
             }