obelieve

# Summary Fixes https://github.com/langgenius/dify/issues/20081 Fixes https://github.com/langgenius/dify/issues/19219 Fixes https://github.com/langgenius/dify/issues/20346 Reason: The `ModelPosition` definition in the following file is of type `Optional[list[str]]`: https://github.com/langgenius/dify-plugin-sdks/blob/main/python/dify_plugin/entities/model/provider.py#L156 Whereas in `api/../provider_entities.py`, the `position` is defined as `list[str]`...