perform this only once

https://github.com/mosure/bevy_zeroverse/blob/7c7918c27390fdd98d7363f7dd732688045ea7f9/ffi/python/test.py#L128

```python

            scene_type='room',
        )

        # TODO: perform this only once
        self.chunk_paths = chunk_and_save(
            self.dataset,
            self.output_dir / 'chunk',

```