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

test/unit/test_holdable_item.gd

@@ -69,3 +69,33 @@ func test_holdable_item_detach_preserves_global_position() -> void:
 	var hand_pos: Vector2 = character.get_node("HandLeft").global_position
 	item._on_drag_picked_up(hand_pos)
 	assert_eq(item.global_position, hand_pos)
+
+
+func test_try_return_to_chest_false_when_no_home_chest() -> void:
+	var item: HoldableItem = HoldableItem.new()
+	add_child_autofree(item)
+	assert_false(item._try_return_to_chest())
+
+
+func test_try_return_to_chest_false_when_beyond_radius() -> void:
+	var chest: RoomChest = RoomChest.new()
+	chest.chest_id = "reception_desk"
+	add_child_autofree(chest)
+	chest.global_position = Vector2.ZERO
+	var item: HoldableItem = HoldableItem.new()
+	add_child_autofree(item)
+	item.home_chest = chest
+	item.global_position = Vector2(200.0, 0.0)
+	assert_false(item._try_return_to_chest())
+
+
+func test_try_return_to_chest_true_when_within_radius() -> void:
+	var chest: RoomChest = RoomChest.new()
+	chest.chest_id = "reception_desk"
+	add_child_autofree(chest)
+	chest.global_position = Vector2.ZERO
+	var item: HoldableItem = HoldableItem.new()
+	add_child_autofree(item)
+	item.home_chest = chest
+	item.global_position = Vector2(40.0, 0.0)
+	assert_true(item._try_return_to_chest())