fix: embed _find_file into generated scripts

add_extra_model_paths() uses _find_file() which must be available in
generated standalone scripts.  Add it to generated_helpers __all__ so the
render step embeds it alongside the other runtime helpers.

comfyui_to_python/generator/generated_helpers.py

@@ -1,4 +1,5 @@
 from ..node_runtime import (
+    _find_file,
     _find_from_extension_location,
     _is_comfyui_directory,
     _load_module,
@@ -13,6 +14,7 @@ from ..node_runtime import (
 )
 
 __all__ = [
+    "_find_file",
     "_find_from_extension_location",
     "_is_comfyui_directory",
     "_load_module",