Reorganize the codebase into role-based folders (snake_case)

Move the 40-odd root-level scripts and scenes into a tree that groups by role,
per the approved roadmap (WS2/WS3): actors/{player,matador,bear}, systems/{combat,
fx,input,debug,render,crowd,config}, ui/, props/ (was tscn_s/). Rename the shell
scene.tscn -> levels/game_shell.tscn and every PascalCase scene to snake_case
(Player.tscn -> player.tscn, MainMenu.tscn -> main_menu.tscn, etc.) so the
case-insensitive web/macOS filesystems can't alias two files together.

Done as a scripted move: each file travels with its .uid; every quoted res:// path
across scenes, scripts, .tres, and project.godot's 9 autoloads is rewritten; the
.godot uid/class cache is rebuilt from scratch. Scenes still resolve by uid, so the
rewrite is belt-and-suspenders. Lint globs (run_tests.sh + both CI workflows) now
walk the new dirs; an orphan animation_tree.gd.uid and 7 pre-existing trailing-
whitespace lints (barrel/torch, never covered by the old root-only glob) are cleaned.

Full suite green on both sides. Asset consolidation (Assets/Animations/fonts ->
art/) is deferred — moving imported .glb/.png/.ttf is safer done in the editor.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017KoYBYQgRyY1zDHXMsXY3V

levels/run_state.gd

@@ -12,7 +12,7 @@ signal run_started
 
 # Every level loads the same reusable shell (player, camera, HUD, PS1 filter); the shell
 # then instances the level's own `level_scene` module into its LevelRoot.
-const _SHELL_SCENE := "res://scene.tscn"
+const _SHELL_SCENE := "res://levels/game_shell.tscn"
 const _ARENA_LEVEL := preload("res://levels/arena_level.tscn")
 const _BEAR_LEVEL := preload("res://levels/bear_level.tscn")
 const _LOBBY_LEVEL := preload("res://levels/lobby_level.tscn")
@@ -53,7 +53,7 @@ const BONUS_HP_CAP: int = 2
 # (its geometry + spawners) and the opponent. The arena (matador wave, normal + boss
 # flavours) and the bear (a lone boss enemy that can turn up as a normal node) live here.
 # Future levels — china shop — slot in the same way: a new module + a LevelDef entry.
-const _BEAR_SCENE := preload("res://Bear.tscn")
+const _BEAR_SCENE := preload("res://actors/bear/bear.tscn")
 
 var _arena: LevelDef
 var _arena_boss: LevelDef