fix: use as cast for HandArea in training_room @onready

src/ui/scenes/training_room.gd

@@ -2,7 +2,7 @@ extends Control
 
 var controller: TrainingController
 
-@onready var hand_area: HandArea = $HandArea
+@onready var hand_area := $HandArea as HandArea
 @onready var play_button: Button = $Buttons/PlayButton
 @onready var pass_button: Button = $Buttons/PassButton
 @onready var hint_button: Button = $Buttons/HintButton