fix: disable echo in the preload file

preload.php

@@ -101,7 +101,9 @@ public function load(): void
                 }
 
                 require_once $file[0];
-                echo 'Loaded: ' . $file[0] . "\n";
+                // Uncomment only for debugging (to inspect which files are included).
+                // Never use this in production - preload scripts must not generate output.
+                // echo 'Loaded: ' . $file[0] . "\n";
             }
         }
     }