feat(战斗系统): 重构子弹追踪逻辑，使用实体当前焦点位置替代鼠标位置

修改所有子弹追踪逻辑，统一使用launcher.currentFocusedPosition作为目标位置
在EntityBase中新增currentFocusedPosition字段，用于存储当前焦点位置
调整MTY角色的攻击距离参数，使用常量定义最小招架和攻击距离

scripts/Statemachine/EntityBase.gd

@@ -108,6 +108,7 @@ var trailing: bool = false
 
 var lastDirection: int = 1
 var currentFocusedBoss: EntityBase = null
+var currentFocusedPosition: Vector2 = Vector2.ZERO
 var charginup: bool = false
 var weapons: Array[Weapon] = []
 var weaponBag: Array[String] = []
@@ -187,6 +188,8 @@ func _physics_process(_delta: float) -> void:
 	if !isPlayer() && !currentFocusedBoss:
 		currentFocusedBoss = MathTool.randomChoiceFrom(get_tree().get_nodes_in_group("players"))
 	animatree.set("parameters/blend_position", lerpf(animatree.get("parameters/blend_position"), lastDirection, 0.2))
+	if is_instance_valid(currentFocusedBoss):
+		currentFocusedPosition = currentFocusedBoss.position
 	if sprinting:
 		if sprintAi():
 			sprinting = false