PyNifly 25.14.0 - HKX skeletons and performance

Native HKX Skeleton Export

• Native skeleton.hkx export for Skyrim LE, SE, and Fallout 4. Skeleton files are now written directly in binary HKX format without requiring hkxcmd. Supports all vanilla skeleton features: bone hierarchy, reference poses, lockTranslation flags, floatSlots, and referenceFloats.

  Previously, I've noted that the round trip probably loses important skeleton data. This release maintains all the data that I know of. See docs/hkx_skeleton_format.md and [docs/hkx_skeleton_format_fo4.md] docs/hkx_skeleton_format_fo4.md) for the details. If you see anything there that you know is wrong or missing, let me know.

• Bone ordering preserved on export. The original HKX bone order is stored on import and restored on export, ensuring animation compatibility (animations reference bones by index).

Performance

• Significant performance enhancements. We've optimized the code in several areas. In particular, Blender 5.1 introduced a ~400x slowdown in per-element UV layer access. UV creation now uses foreach_set for bulk assignment, restoring import speed on 5.1 and slightly improving earlier versions as well.

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