Fix pyright errors in node-factory.py

[sanleo-wq]

Fixed the type handling in the _arguments_as_outputs method:

• Used isinstance(argument, Output) instead of issubclass(type(argument), Output) for proper instance checking
• Added explicit type cast for better type inference

Added proper type annotations and documentation:

• Added docstring to the base add_extension method
• Added explicit typing information to improve Pyright's type inference

Updated the corresponding stub file node_factory.pyi for consistency with the implementation:

• Fixed type annotations in method signatures
• Improved docstrings to match the implementation

These changes resolve the Pyright errors related to type inconsistencies and improve the overall type safety of the code.

Fixes #30153