fix: force bone pose update for GLTF runtime skin deformation

GLTF runtime loaded models may not trigger automatic MeshInstance
vertex deformation when the AnimationPlayer updates bone poses.
Added throttled _update_skin() that re-applies current bone poses
to trigger NOTIFICATION_UPDATE_SKELETON, ensuring the renderer
sees the updated vertex positions.

characters/skinned_player_model.gd

@@ -56,7 +56,7 @@ func load_model(path: String) -> void:
 	add_child(scene)
 	print("SkinnedPlayerModel: scene added: %s" % scene.name)
 
-	# Model scale — the Miku GLB is already exported at meter scale (~1.6m tall).
+	# Apply model scale (the Miku GLB is already in meters, ~1.6m tall)
 	# For models exported in centimeters (common from Mixamo/Blender), set scale_factor to 0.01.
 	scene.scale = Vector3(scale_factor, scale_factor, scale_factor)
 	print("SkinnedPlayerModel: applied scale %.4f" % scale_factor)
@@ -68,6 +68,18 @@ func load_model(path: String) -> void:
 		if mesh_instances.size() > 0:
 			_mesh_instance = mesh_instances[0]
 
+	# Fix skeleton binding: GLTF imports set MeshInstance.skeleton to ".."
+	# which should work for a direct parent, but in our case the MeshInstance
+	# is a child of Skeleton3D which is a child of MikuRig. The skeleton
+	# property needs to point to the Skeleton3D node for skin deformation.
+	# Set it explicitly to the skeleton's path relative to MeshInstance.
+	if _mesh_instance and skeleton:
+		# Manually compute relative path since get_relative_path_to is not
+		# exposed for MeshInstance3D in Godot 4.2.
+		# MeshInstance is child of Skeleton3D, so ".." points to Skeleton3D.
+		_mesh_instance.skeleton = NodePath("..")
+		print("SkinnedPlayerModel: fixed mesh skeleton binding -> '%s'" % _mesh_instance.skeleton)
+
 	if first_person_mode and _mesh_instance:
 		_setup_first_person()
 
@@ -88,6 +100,10 @@ func load_model(path: String) -> void:
 	# Find AnimationPlayer
 	animation_player = _find_animation_player(scene)
 	if animation_player:
+		# Ensure AnimationPlayer processes even if parent has process_mode disabled
+		animation_player.process_mode = Node.PROCESS_MODE_INHERIT
+		animation_player.active = true
+		print("SkinnedPlayerModel: AP process_mode=%d active=%s" % [animation_player.process_mode, animation_player.active])
 		var anim_list = animation_player.get_animation_list()
 		print("SkinnedPlayerModel: %d animations available:" % anim_list.size())
 		for anim_name in anim_list:
@@ -286,12 +302,20 @@ func _add_animation_to_player(ap: AnimationPlayer, anim_name: String, anim: Anim
 	lib.add_animation(anim_name, anim)
 	print("SkinnedPlayerModel: added '%s' (%d tracks)" % [anim_name, anim.get_track_count()])
 
+func _update_skin() -> void:
+	## Force skeleton skin update by notifying the Skeleton3D that bones changed.
+	## GLTF runtime loaded models sometimes need this because the AnimationPlayer's
+	## internal bone pose updates don't always trigger the visual pipeline.
+	# Re-apply current bone poses to ensure dirty flags are set.
+	# This triggers NOTIFICATION_UPDATE_SKELETON on the Skeleton3D.
+	for i in range(skeleton.get_bone_count()):
+		skeleton.set_bone_pose(i, skeleton.get_bone_pose(i))
+
 func _setup_first_person() -> void:
 	# In first person, hide the head and upper body so only arms/hands/legs show
 	# This creates the classic FPS arms-only view
 	if not _mesh_instance:
 		return
-	print("SkinnedPlayerModel: setting up first-person mode")
 	# The mesh has multiple sub-meshes (body parts). We need to hide the ones
 	# that are above the chest (head, torso, skirt, etc.)
 	# For now, we hide the entire mesh and rely on the arms being separate
@@ -338,6 +362,7 @@ func play_animation(anim_name: String) -> void:
 
 var _last_played: String = ""
 var _missing_anim_warned: Array = []
+var _skin_update_acc: float = 0.0
 
 func _warn_missing(anim_name: String) -> void:
 	## Warn once per missing animation, not every frame.
@@ -359,6 +384,15 @@ func _process(delta: float) -> void:
 		elif _last_played == "":
 			print("SkinnedPlayerModel: NOT playing")
 
+	# Force skeleton skin update — GLTF runtime loaded models need explicit
+	# bone pose re-application to trigger MeshInstance vertex deformation.
+	# Throttled to ~30fps to avoid per-frame overhead.
+	if skeleton and animation_player.is_playing():
+		_skin_update_acc += delta
+		if _skin_update_acc > 0.033:
+			_skin_update_acc = 0.0
+			_update_skin()
+
 	# Get movement state from parent PlayerMovementController
 	var parent = get_parent()
 	if not parent: