feat(rooms): add RoomChest nodes to Floor 0 rooms

ReceptionDesk, GiftShopShelf, RestaurantCounter, EmergencyCabinet added
to their respective tscn files. Fixes spawn_items deferred call to avoid
add_child race during _ready tree setup.

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

test/unit/test_room_chests_floor0.gd

@@ -0,0 +1,54 @@
+## Tests for RoomChest presence and item counts in Floor 0 rooms.
+extends GutTest
+
+
+func test_reception_has_chest_reception_desk() -> void:
+	var room: Node = preload("res://scenes/rooms/floor0/Reception.tscn").instantiate()
+	add_child_autofree(room)
+	assert_not_null(room.get_node_or_null("ReceptionDesk"))
+
+
+func test_reception_desk_has_three_items() -> void:
+	var room: Node = preload("res://scenes/rooms/floor0/Reception.tscn").instantiate()
+	add_child_autofree(room)
+	var chest: RoomChest = room.get_node_or_null("ReceptionDesk") as RoomChest
+	assert_eq(chest.get_item_config_count(), 3)
+
+
+func test_giftshop_has_chest_giftshop_shelf() -> void:
+	var room: Node = preload("res://scenes/rooms/floor0/GiftShop.tscn").instantiate()
+	add_child_autofree(room)
+	assert_not_null(room.get_node_or_null("GiftShopShelf"))
+
+
+func test_giftshop_shelf_has_three_items() -> void:
+	var room: Node = preload("res://scenes/rooms/floor0/GiftShop.tscn").instantiate()
+	add_child_autofree(room)
+	var chest: RoomChest = room.get_node_or_null("GiftShopShelf") as RoomChest
+	assert_eq(chest.get_item_config_count(), 3)
+
+
+func test_restaurant_has_chest_restaurant_counter() -> void:
+	var room: Node = preload("res://scenes/rooms/floor0/Restaurant.tscn").instantiate()
+	add_child_autofree(room)
+	assert_not_null(room.get_node_or_null("RestaurantCounter"))
+
+
+func test_restaurant_counter_has_three_items() -> void:
+	var room: Node = preload("res://scenes/rooms/floor0/Restaurant.tscn").instantiate()
+	add_child_autofree(room)
+	var chest: RoomChest = room.get_node_or_null("RestaurantCounter") as RoomChest
+	assert_eq(chest.get_item_config_count(), 3)
+
+
+func test_emergency_has_chest_emergency_cabinet() -> void:
+	var room: Node = preload("res://scenes/rooms/floor0/EmergencyRoom.tscn").instantiate()
+	add_child_autofree(room)
+	assert_not_null(room.get_node_or_null("EmergencyCabinet"))
+
+
+func test_emergency_cabinet_has_three_items() -> void:
+	var room: Node = preload("res://scenes/rooms/floor0/EmergencyRoom.tscn").instantiate()
+	add_child_autofree(room)
+	var chest: RoomChest = room.get_node_or_null("EmergencyCabinet") as RoomChest
+	assert_eq(chest.get_item_config_count(), 3)