Blender flattening support

[dmitry-mli]

What

• Implemented flattening logic that uses conformal UV unwrap in cortex.blender.blendlib.py. It follows the same selection as for the volume mesh. This is accessible via write_flat_patch.
  • To avoid confusion between the new flat patch write_flat_patch and the old one, renamed save_patch into write_volume_patch.
  • Renamed _get_pts_edges into _get_geometry for clarity. Added clarifying logging and elapsed time tracking. Extended docstring.
• Fix for Python 3.13+: allow blender access Python site directory to search for mda_xdrlib that was removed from Python 3.13.
• Refactored cortex.blender._call_blender to support non-code calls to Blender to reduces confusion and improves code clarity. Refactored fs_cutintofs_cut_initand added a newfs_cut_open` to improve clarity. Extended docstring.
• Rewrote cut_surface for clarity. Onboarded to recache flag to support forced generation.
• Record a tutorial video walking users through the process of cutting. Should follow the gallantlab.org approach to cutting.
• Add python notebook for the end-to-end rendering of fMRI.
• Update docs with the guidance.
  • Fixed the existing docs confusing ” and " which may result into code examples not running properly.
• Address the PR feedback.

Tutorial video

As different labs may approach cuts slightly differently, created and edited a tutorial video instruction that follows the style of gallantlab.org. The used anatomy was taken from Horikawa, T., Cowen, A. S., Keltner, D., & Kamitani, Y. (2020). The neural representation of visually evoked emotion is high-dimensional, categorical, and distributed across transmodal brain regions..

Docs update

Added a new section on the cuts. When rendered looks as follows:

[cmcneil]

Looks pretty good to me! Minor nits, but seems like an overall generalization with some improvements to code quality.