feat(items): add chest-return priority to HoldableItem and GameState v3 chest states

- HoldableItem._try_return_to_chest() snaps item back if within CHEST_RETURN_RADIUS (80px)
- _on_drag_released checks chest return before hand-slot fallback
- OutfitItem._on_drag_released checks chest return before outfit/hand-slot logic
- GameState: _chest_states dict + get/set/clear_chest_state methods
- GameState.get_save_data() bumped to version 3, includes chest_states
- GameState.apply_save_data() restores chest_states from save data

scripts/objects/holdable_item.gd

@@ -7,6 +7,7 @@ signal item_picked_up(item: HoldableItem)
 signal item_placed(item: HoldableItem)
 
 const HAND_SLOT_RADIUS: float = 60.0
+const CHEST_RETURN_RADIUS: float = 80.0
 
 @export var item_id: String = ""
 
@@ -27,6 +28,8 @@ func _on_drag_picked_up(_pos: Vector2) -> void:
 
 
 func _on_drag_released(_pos: Vector2) -> void:
+	if _try_return_to_chest():
+		return
 	var result: Array = _find_nearest_free_hand_slot()
 	if not result.is_empty():
 		var character: Character = result[0] as Character
@@ -35,6 +38,15 @@ func _on_drag_released(_pos: Vector2) -> void:
 	item_placed.emit(self)
 
 
+func _try_return_to_chest() -> bool:
+	if home_chest == null:
+		return false
+	if global_position.distance_to(home_chest.global_position) >= CHEST_RETURN_RADIUS:
+		return false
+	(home_chest as RoomChest).receive_item(self)
+	return true
+
+
 func is_in_hand_slot() -> bool:
 	var p: Node = get_parent()
 	if p == null:

scripts/objects/outfit_item.gd

@@ -10,6 +10,8 @@ const OUTFIT_APPLY_RADIUS: float = 80.0
 
 
 func _on_drag_released(_pos: Vector2) -> void:
+	if _try_return_to_chest():
+		return
 	var character: Character = _find_nearest_character()
 	if character != null:
 		character.apply_outfit_item(outfit_layer, item_id, outfit_sprite, self)