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

systems/combat/physics_layers.gd

@@ -0,0 +1,11 @@
+## Central registry of the 3D physics collision-layer bits. These mirror the
+## layer_names in project.godot so the editor's layer picker reads the same words.
+##
+## The bull only collides with WORLD, so a killed matador is lifted off WORLD onto
+## CORPSE alone (see matador_ragdoll.gd). The ground and walls carry WORLD | CORPSE
+## (tagged at level load in game_shell.gd), so the ragdoll still rests on the arena
+## while the bull passes through the bodies instead of tripping over them.
+
+const WORLD:  int = 1  # layer 1 — environment + live actors (bull, matadors, spears)
+const BULL:   int = 2  # layer 2 — the bull's own body
+const CORPSE: int = 4  # layer 3 — ragdolled matadors; ground/walls also carry this