feat(ChainGun): 为链式机枪添加子弹数量属性并调整子弹生成逻辑

修改链式机枪的武器脚本、场景配置和子弹脚本，新增count属性控制子弹数量
子弹生成时根据count值调整位置分布，同时更新UI描述文本

scripts/Contents/Weapons/ChainGun.gd

@@ -3,7 +3,9 @@ extends Weapon
 
 func update(to, origin, _entity):
 	origin["atk"] += 2 * to * soulLevel
+	origin["count"] += 0.25 * to * soulLevel
 	return origin
 func attack(entity: EntityBase):
 	for i in BulletBase.generate(ComponentManager.getBullet("ChainGun"), entity, entity.texture.global_position, (get_global_mouse_position() - entity.texture.global_position).angle()):
 		i.damage = readStore("atk")
+		i.count = floor(readStore("count"))