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

tests/bear_fx_test.gd

@@ -1,6 +1,6 @@
 extends SceneTree
 ## Bear attack-FX test. The four attack effects (crater, smash debris, left/right claw slash)
-## live in Assets/fx/Bear_FX.glb as meshes that rest at scale 0 at Siim's baked positions. The
+## live in art/fx/bear_fx.glb as meshes that rest at scale 0 at Siim's baked positions. The
 ## GLB carries its own AnimationPlayer whose clips scale one mesh up at its strike frame and
 ## back to 0 (self-hiding) while pinning the others at 0. bear.gd fires the matching clip on
 ## each strike (see _play_fx). This asserts each clip pops its own mesh, self-hides by the end,
@@ -27,7 +27,7 @@ func _ok(c: bool, m: String) -> void:
 
 
 func _run() -> void:
-	var bear := (load("res://Bear.tscn") as PackedScene).instantiate()
+	var bear := (load("res://actors/bear/bear.tscn") as PackedScene).instantiate()
 	root.add_child(bear)
 	await physics_frame