【引擎触发】closedbagitemclick：背包扩容格的解锁引导

---closedbagitemclick: 点击未开启格子触发
function closedbagitemclick(actor, slotIndex)
    local player = class(actor)
    if not player then return end
    -- 前两排格子靠任务解锁
    if slotIndex <= 48 then
        sendmsg(actor, 1, "完成「行商的委托」任务可解锁此格")
        callscript(actor, "guide_bag_task")
        return
    end
    -- 后排格子用元宝开启：价格阶梯
    local price = 100 + (slotIndex - 48) * 50
    sendmsg(actor, 1, "花费 " .. price ..
        " 元宝可永久开启此格，双击确认")
    Bag.unlockPrompt(actor, slotIndex, price)
end

---格子解锁的确认与结算
function Bag.unlock(actor, slotIndex, price)
    local player = class(actor)
    if not player then return false end
    -- 幂等：已解锁的格子拒绝重复购买
    if Bag.isUnlocked(actor, slotIndex) then
        sendmsg(actor, 1, "该格子已开启")
        return false
    end
    if not Bag.takeYuanbao(actor, price) then
        sendmsg(actor, 1, "元宝不足")
        return false
    end
    setplayvar(actor, "HUMAN", "BagSlot_" .. slotIndex, 1, 1)
    sendmsg(actor, 1, "格子已永久开启！")
    playsound(actor, 1020)
    return true
end