feat: 添加掉落物功能，更新饲料和物品显示，重构相关UI组件

scripts/Statemachine/UIState.gd

@@ -1,9 +1,17 @@
 extends CanvasLayer
 class_name UIState
 
+@onready var baseball = $"%baseball"
+@onready var basketball = $"%basketball"
+
+static var player: EntityBase = null
 static var bossbar: EntityStateBar
 
 func _ready():
 	bossbar = $"%bossbar"
 func _process(_delta):
 	bossbar.visible = !!bossbar.entity
+func _physics_process(_delta):
+	if is_instance_valid(player):
+		baseball.count = player.inventory[ItemStore.ItemType.BASEBALL]
+		basketball.count = player.inventory[ItemStore.ItemType.BASKETBALL]