Add curated obj demo set (19 species) to match local demo

Dance sample: add n2.mp4 (with audio), drop wulin2.mp4

Add _ffs.bvh template for all obj characters (fixes BVH/GLB export)

Add retarget-source bvh for all sample species (part 2)

Add retarget-source bvh for all sample species

Super-squash branch 'main' using huggingface_hub