【网络通信】广播优化：AOI 视野内的增量推送

---广播范围收敛：以动作为圆心的视野格
local VIEW = 8   -- 视野 8 格

function Broadcast.area(mapId, x, y, msg)
    local sent = 0
    for _, actor in ipairs(Map.onlineActors(mapId)) do
        local dx = actor.x - x
        local dy = actor.y - y
        if dx * dx + dy * dy <= VIEW * VIEW then
            sendmsg(actor, 3, msg)   -- 类型 3：当前地图定向
            sent = sent + 1
        end
    end
    Broadcast.metrics(mapId, sent)
end

---状态快照：只推变化的角色数据
setontimerex(60, 1)
function Broadcast.deltaTick(mapId)
    for _, actor in ipairs(Map.onlineActors(mapId)) do
        local snap = Snap.of(actor)
        local prev = Snap.prev(actor)
        if snap.hp ~= prev.hp or snap.buff ~= prev.buff then
            local view = Snap.viewOf(actor)
            for _, watcher in ipairs(view) do
                Msg.send(watcher, "STATE", snap.id,
                    snap.hp, snap.buff)
            end
            Snap.save(actor)
        end
    end
end