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

tools/preview_crowd_scene.gd

@@ -13,7 +13,7 @@ func _init() -> void:
 
 func _run() -> void:
 	DirAccess.make_dir_recursive_absolute(OUT)
-	var ps := load("res://scene.tscn") as PackedScene
+	var ps := load("res://levels/game_shell.tscn") as PackedScene
 	var scene := ps.instantiate()
 	root.add_child(scene)
 	current_scene = scene