Lua协程包装：wrap与create的取舍

-- 错误：resume 失败不查状态，静默中断
local co = coroutine.create(body)
local ok = coroutine.resume(co)
if ok then
    markDone()
end

local body = function(total)
    for i = 1, total do
        buildOne(i)
        coroutine.yield(i)
    end
end
local step = coroutine.wrap(body)
local p = getplayerbyname("cor01")
for _ = 1, 3 do
    local ok, val = pcall(step)
    if not ok then break end
end
sendmsg(p, 1, "分帧推进完成")