fix(core): remove class_name from autoload scripts to prevent singleton conflict

Godot 4 throws "Class hides an autoload singleton" when a script declares
class_name with the same name as its registered autoload. Removed class_name
from AudioManager and RoomNavigator — both are accessible globally via their
autoload name without it. Also ignores Godot-generated *.uid files.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -3,6 +3,7 @@
 # Godot generated files
 .godot/
 .import/
+*.uid
 
 # Godot-specific ignores
 export.cfg