feat(子弹系统): 添加子弹追踪功能

在EntityBase.gd中添加BULLET_TRACE字段，并在BulletBase.gd中实现追踪逻辑。FieldStore.gd中新增BULLET_TRACE枚举及相关配置，支持百分比类型的追踪强度设置

scripts/Statemachine/BulletBase.gd

@@ -59,6 +59,15 @@ func _physics_process(_delta: float) -> void:
 	if destroying: return
 	if is_instance_valid(launcher) and (launcher.isPlayer() or is_instance_valid(launcher.currentFocusedBoss)):
 		launcher.position -= Vector2.from_angle(rotation) * recoil
+		PresetAIs.trace(
+			self,
+			EntityTool.findClosetEntity(position, get_tree(),
+			!launcher.isPlayer(),
+			launcher.isPlayer(),
+			[launcher]
+			).position,
+			launcher.fields.get(FieldStore.Entity.BULLET_TRACE) / 10
+		)
 		ai()
 	else:
 		tryDestroy()

scripts/Statemachine/EntityBase.gd

@@ -26,6 +26,7 @@ var fields = {
 	FieldStore.Entity.EXTRA_BULLET_COUNT: 0,
 	FieldStore.Entity.BULLET_SPLIT: 0,
 	FieldStore.Entity.BULLET_REFRACTION: 0,
+	FieldStore.Entity.BULLET_TRACE: 0,
 	"速度": TITLE_FLAG,
 	FieldStore.Entity.MOVEMENT_SPEED: 1,
 	FieldStore.Entity.ATTACK_SPEED: 1,