【后端接口】决斗申请：切磋邀请与胜负裁决

---决斗邀请：30 秒确认窗口
function Duel.invite(actor, targetName)
    local player = class(actor)
    if not player then return false end
    local target = getplayerbyname(targetName)
    if not target then return false end
    if not Duel.inRange(actor, target, 5) then
        sendmsg(actor, 1, "走近些再发起切磋（5 格内）")
        return false
    end
    -- 对方的决斗确认窗口
    local key = "DuelFrom_" .. actor
    setplayvar(target, "HUMAN", key, os.time(), 0)
    sendmsg(target, 1, actor .. " 发来切磋邀请，30 秒内回复")
    sendmsg(actor, 1, "切磋邀请已发出，等待对方应答")
    return true
end

---playdie: 切磋中的死亡走决斗裁决
function Duel.judge(self, hiter)
    local player = class(self)
    if not player then return end
    if not Duel.inDuel(self, hiter) then return end
    -- 切磋死亡：无掉落、无 PK 值、原地满血复活
    humanhp(self, "=", self:GetMaxHp())
    mapmove(self, self.mapId, self.x + 1, self.y, 0)
    sendmsg(nil, 1, "切磋结果：" .. hiter:GetName() ..
        " 战胜了 " .. self:GetName())
    Duel.clear(self)
    Duel.clear(hiter)
end