fix: use animated GLB with all locomotion animations and fix scaling

The skinned player model was loading miku_rigged_final.glb which only
contained a single "Idle" animation (1 track, near-rest pose). This caused
"animation 'Jump/Walk/Run' not found" spam and a T-pose appearance.

Switch to miku_rigged_animated.glb which has all 7 animations
(Crouch, Death, Idle, Idle2, Jump, Run, Walk).

Additional fixes:
- Fix scaling: the GLB is already in meters (~1.6m tall), not cm.
  Removed the unconditional 0.01 cm->m conversion that was shrinking
  the character to 1/100th size.
- Fix bone track paths: use "MikuRig/Skeleton3D:" prefix matching the
  actual scene tree structure (AnimationPlayer is sibling of MikuRig).
- Add _ensure_locomotion_animations() to create Walk/Run/Jump/Idle
  procedurally if the GLB is missing them.
- Eliminate per-frame "not found" log spam with rate-limited warnings.
- Update level_runtime.gd and test_level_builder.gd to use animated GLB.

Closes #3d-player-model animation pipeline

debug/test_level_builder.gd

@@ -432,7 +432,7 @@ func _spawn_player(pid: int) -> CharacterBody3D:
 		# Miku: use the rigged GLB model with its own armature
 		var skinned = load("res://characters/skinned_player_model.gd").new()
 		skinned.name = "SkinnedModel"
-		skinned.model_path = "res://assets/characters/skins/miku_rigged_final.glb"
+		skinned.model_path = "res://assets/characters/skins/miku_rigged_animated.glb"
 		skinned.scale_factor = 1.0  # Already scaled to 1.8m in Blender
 		skinned.position = Vector3.ZERO  # Model origin = player origin
 		player.add_child(skinned)