SkinnedPlayerModel:
- Added _print_tree debug to see GLB scene structure at runtime
- Auto-play Idle animation on load
- Added periodic debug output for animation state
- Only change animation when target differs from current
Third-person camera:
- F1 toggles between FPS and third-person view
- Third-person camera positioned behind/above player
- Smooth follow with lerp
- Camera tracks player position each frame