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

art/materials/barrel_metal.tres

@@ -0,0 +1,5 @@
+[gd_resource type="StandardMaterial3D" format=3 uid="uid://b73nb47y8ppt"]
+
+[resource]
+albedo_color = Color(0.26098922, 0.27367952, 0.27059656, 1)
+metallic = 1.0

art/materials/barrel_wood.tres

@@ -0,0 +1,4 @@
+[gd_resource type="StandardMaterial3D" format=3 uid="uid://isrp2y47xs5x"]
+
+[resource]
+albedo_color = Color(0.49425018, 0.31969637, 0.21259204, 1)

art/materials/bear_claw_fx.tres

@@ -0,0 +1,5 @@
+[gd_resource type="StandardMaterial3D" format=3 uid="uid://blpkmyikjnhbo"]
+
+[resource]
+emission_enabled = true
+emission = Color(0.4627451, 0.8117647, 0.9490196, 1)

art/materials/fire.tres

@@ -0,0 +1,5 @@
+[gd_resource type="StandardMaterial3D" format=3 uid="uid://dgmk764033feq"]
+
+[resource]
+emission_enabled = true
+emission = Color(0.7096375, 0.3347874, 0.09943161, 1)