Reorganize into role-based folders and consolidate art

Move every script and scene into role-based directories (actors/, systems/, ui/,
levels/, props/) and all raw art under art/ (grouped by role, snake_case,
Extract-Textures GLBs), dropping Blender version-suffix noise. Filenames are
snake_case (PascalCase reserved for class_name) to avoid case-insensitive
filesystem aliasing on the web/macOS targets. Routes the bull's hits through the
typed DamageEvent pipeline and wires the bull's abilities to the Fx library.
Updates CLAUDE.md's folder-layout overview to match.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CCyaJPTHCH9EDthpf4A5Sj

levels/game_shell.gd

@@ -4,7 +4,7 @@ extends Node3D
 ## spawners, lighting, colliders) into LevelRoot. Switching levels frees the whole
 ## previous module first, so no old mesh or collider can survive into the next fight.
 
-const PhysicsLayers = preload("res://physics_layers.gd")
+const PhysicsLayers = preload("res://systems/combat/physics_layers.gd")
 
 @onready var _level_root: Node3D = $LevelRoot
 @onready var _camera: IsoCamera = $Player/Camera3D