[fix] overhaul plotvolume slice viewer and speed up matplotlib rendering, bump 0.6.5

plotvolume (mcxplotvol-style viewer):
- robust slice picking via forward projection + exact per-pixel depth (replaces
  fragile inverse-projection ray-casting that often selected the wrong slice).
- slice3i-style dragging (move along the slice normal projected to screen).
- rotation direction now matches MATLAB rotate3d (drag right -> azimuth down,
  drag up -> elevation down).
- remove the bottom sliders; the 3D axes now fills/resizes with the window.
- up/down arrows switch frames for any 4-D array (like mcxplotvol changeframe),
  with a frame indicator in the title.
- right-button drag changes the colormap level count, matching slice3i
  (relative to the level at drag start, ~64 levels per full-window drag).
- vectorized slice polygon/color build + coarse level-of-detail while
  interacting (~15x faster dragging on large volumes).
- auto-show on construction; fix cm.get_cmap removal (matplotlib 3.9);
  fix shade=True crash with edgecolors='none'.
- match plotmesh colormap convention: cmap= keyword, default jet (colormap=
  kept as a back-compat alias).

plotsurf/plotasurf/plottetra:
- vectorize per-face vertex and color construction (~84x faster on large
  surfaces); remove redundant face-value recomputations and an ndarray
  truthiness landmine.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: fangq

README.md

@@ -4,7 +4,7 @@
 
 * **Copyright**: (C) Qianqian Fang (2024-2025) <q.fang at neu.edu>
 * **License**: GNU Public License V3 or later
-* **Version**: 0.6.3
+* **Version**: 0.6.5
 * **URL**: [https://pypi.org/project/iso2mesh/](https://pypi.org/project/iso2mesh/)
 * **Homepage**: [https://iso2mesh.sf.net](https://iso2mesh.sf.net)
 * **Github**: [https://github.com/NeuroJSON/pyiso2mesh](https://github.com/NeuroJSON/pyiso2mesh)

iso2mesh/__init__.py

@@ -264,7 +264,7 @@
     ndimfilter,
 )
 
-__version__ = "0.6.3"
+__version__ = "0.6.5"
 __all__ = [
     "advancefront",
     "barycentricgrid",