feat: add rigged+animated Miku player model with auto-rig pipeline

- Add miku_rigged_animated.glb (3.27MB) with 18-bone skeleton and 6 animations
  (Idle, Walk, Run, Jump, Crouch, Death) via Blender auto-rig script
- Add tools/rig_and_animate.py: reusable Blender script for rigging any humanoid
  mesh with Mixamo-compatible bone naming
- Update SkinnedPlayerModel: scale_factor, first-person mode, animation state
  matching (Idle/Walk/Run/Jump/Crouch/Death)
- Update level_runtime.gd: use skinned model for local player, procedural
  humanoid for remote players
- Update skin_manager.gd and test_level_builder.gd to use animated model
- Fix Godot 4.2.1 'is not Type' syntax in 5 weapon files
- Add editor/import_miku_to_tscn.gd for editor-based GLB import

debug/test_level_builder.gd

@@ -432,7 +432,8 @@ 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)
 	else: