【框架设计】配置热重载：监听回调与失败回滚的框架设计

local CONFIGS = {
    drop_rate = { value = 100, check = function(v) return v >= 50 and v <= 300 end },
    war_time = { value = 3600, check = function(v) return v >= 600 and v <= 14400 end },
}
local function applyConfig(name, newVal)
    local cfg = CONFIGS[name]
    if cfg == nil then
        return false, "未知配置"
    end
    if not cfg.check(newVal) then
        return false, "校验失败:" .. name
    end
    cfg.old = cfg.value
    cfg.value = newVal
    return true
end

local function rollbackConfig(name)
    local cfg = CONFIGS[name]
    if cfg ~= nil and cfg.old ~= nil then
        cfg.value, cfg.old = cfg.old, cfg.value
        setsysvarex("CFG_RB_" .. name, cfg.value, 1)
        return true
    end
    return false
end