【网络通信】会话续期握手：SL:Schedule静默探测与心跳保活

local lastRecv = os.time()
SL:RegisterLuaNetMsg(9000, function(data)
    lastRecv = os.time()
end)
SL:Schedule(function()
    if os.time() - lastRecv >= 30 and not probing then
        probing = true
        probeAt = os.time()
        SL:SendNetMsg(9001, { t = os.time() })
    end
end, 10)

SL:RegisterLuaNetMsg(9002, function(data)
    lastRecv = os.time()
    probing = false
end)
SL:Schedule(function()
    if probing and os.time() - probeAt >= 60 then
        probing = false
        SL:ShowSystemTips("连接已断开，正在重连")
        reconnect()
    end
end, 5)