【界面UI】技能升级试算面板：模拟试算的界面实现

local function previewUpgrade(curLv, targetLv)
    local perLv = skIncFromServer or 15
    local gain = (targetLv - curLv) * perLv
    local cost = (targetLv - curLv) * 2
    GUI:setText(gainLabel, "伤害加成 +" .. gain)
    GUI:setText(costLabel, "消耗技能书 ×" .. cost .. "、金币" .. cost * 5000)
end

GUI:addOnClickEvent(confirmBtn, function()
    SL:SendNetMsg(9701, { lv = targetLv })
end)
SL:RegisterLuaNetMsg(9702, function(data)
    if data.ok == 1 then
        if data.gain ~= lastGain then
            SL:ShowSystemTips("实际收益与试算有差异，已按实际值更新")
        end
        refreshPanel(data)
    end
end)