feat(miku): proper rigged model from Sketchfab + Blender

Pipeline:
1. Downloaded TDA-style Miku model from Sketchfab (19MB FBX, 38K verts)
2. Imported to Blender, scaled to Godot humanoid proportions (1.8u tall)
3. Created clean 17-bone humanoid armature (Hips/Spine/Chest/Head/Arms/Legs)
4. Auto-weight-painted mesh to armature
5. Added Idle (breath bounce) and Run (cycle) animations
6. Exported as GLB with embedded animations (3MB)

New:
- SkinnedPlayerModel class: loads GLB with own armature+animations
- Player 1 spawns with Miku model, others get procedural humanoid
- Completely separate from procedural model system

Files:
- assets/characters/skins/miku_rigged_final.glb (3MB, 48K verts, 17 bones, 2 anims)
- characters/skinned_player_model.gd
- Removed old procedural GLB attempts

debug/test_level_builder.gd

@@ -369,27 +369,21 @@ func _spawn_player(pid: int) -> CharacterBody3D:
 	if mover_script:
 		player.set_script(mover_script)
 
-	# Humanoid Model for Player
-	var humanoid = load("res://characters/humanoid_model.gd").new()
-	humanoid.name = "HumanoidModel"
-	humanoid.color = Color(0.2, 0.4, 0.8)
-	humanoid.shadows_only = (pid == multiplayer.get_unique_id())
-	humanoid.position = Vector3(0, -0.9, 0)
-	player.add_child(humanoid)
-
-	# Apply skin (Miku for player 1, default for others)
+	# Visual Model for Player
+	# Player 1 gets the Miku skinned model, others get procedural humanoid
 	if pid == 1:
-		var miku_skin = PlayerSkin.new()
-		miku_skin.skin_name = "Miku"
-		miku_skin.model_path = "res://assets/characters/skins/miku_rigged.glb"
-		miku_skin.color_tint = Color(0.0, 0.75, 0.75)
-		humanoid.apply_skin(miku_skin)
+		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.position = Vector3(0, -0.9, 0)
+		player.add_child(skinned)
 	else:
-		# Default blue skin for other players
-		var default_skin = PlayerSkin.new()
-		default_skin.skin_name = "Default"
-		default_skin.color_tint = Color(0.2, 0.4, 0.8)
-		humanoid.apply_skin(default_skin)
+		var humanoid = load("res://characters/humanoid_model.gd").new()
+		humanoid.name = "HumanoidModel"
+		humanoid.color = Color(0.2, 0.4, 0.8)
+		humanoid.shadows_only = (pid == multiplayer.get_unique_id())
+		humanoid.position = Vector3(0, -0.9, 0)
+		player.add_child(humanoid)
 
 	# Movement State Machine
 	var sm := Node.new()