Two fixes from the animation audit:
1. Variant cache key now includes the resolved animation name (e.g., Struggle.2).
Previously, the cache key only used context+parts, so the first random variant
pick was reused forever. Now each variant gets its own cache entry, and a fresh
random pick happens each time the context changes.
2. FullHead check changed from contains("Head") to startsWith("gltf_FullHead")
to prevent false positives on names like FullOverhead or FullAhead.
FullStruggle, FullWalk etc. animate body+legs but preserve head tracking.
FullHeadStruggle, FullHeadWalk etc. also animate the head.
The 'Head' keyword in the animation name is the opt-in signal.
Previously, any GLB with keyframes on free bones would animate them,
even for standard animations like Idle. This caused accidental bone
hijacking — e.g., handcuffs freezing the player's head because the
artist keyframed all bones in Blender.
Now the Full prefix (FullIdle, FullStruggle, FullWalk) is enforced:
only Full-prefixed animations can animate free bones. Standard
animations (Idle, Struggle, Walk) only animate owned bones.
This aligns the code with the documented convention in ARTIST_GUIDE.md.
Strip all Phase references, TODO/FUTURE roadmap notes, and internal
planning comments from the codebase. Run Prettier for consistent
formatting across all Java files.
