refactor(ChainGun): 调整武器属性和子弹生成逻辑

修改ChainGun的数值属性和子弹生成方式，新增split参数控制子弹间距
调整BossBar的样式和位置，删除未使用的shader文件

scripts/Contents/Weapons/ChainGun.gd

@@ -3,9 +3,11 @@ extends Weapon
 
 func update(to, origin, _entity):
 	origin["atk"] += 2 * to * soulLevel
-	origin["count"] += 0.25 * to * soulLevel
+	origin["count"] = 1 * soulLevel
+	origin["split"] /= 1 + 0.05 * 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"))
+		i.split = readStore("split")