Refactor documentation sidebar paths to reflect how objects are imported in package structure

<img width="990" height="312" alt="Image" src="https://github.com/user-attachments/assets/ecc2a8ac-5a02-413e-9a1c-3aa58abb14b8" />

I do `from nglui.statebuilder import ViewerState`, think the docs should probably mirror that kind of thing. User doesn't need to know about `base.py`-type distinctions