fix: handle SerializableClosure in action column display

Routes using Laravel's SerializableClosure (e.g., the storage/{path}
route from FilesystemServiceProvider) are not instances of \Closure,
so the instanceof check falls through and the serialized closure object
is displayed as a string.

Use is_string() to check whether the action is a controller reference;
anything else (Closure, SerializableClosure, etc.) displays as "Closure".

Author: alies-dev

src/Http/Controllers/Api.php

@@ -32,7 +32,7 @@ public function getRoutes()
                 'uri' => $route->uri,
                 'as' => $routeName,
                 'methods' => $route->methods,
-                'action' => $route->action['uses'] instanceof \Closure ? 'Closure' : ($route->action['uses'] ?? ''),
+                'action' => is_string($route->action['uses'] ?? '') ? ($route->action['uses'] ?? '') : 'Closure',
                 'middleware' => $routeMiddleware,
             ];
         })->values()->all();