【数据存储】战斗录像分段存储：录像索引与过期清理

local function saveSeg(rid, segId, payload)
    setsysvar("REC_" .. rid .. "_" .. segId, payload)
    local idx = getsysvar("REC_IDX_" .. rid) or ""
    if idx == "" then
        idx = tostring(segId)
    else
        idx = idx .. "," .. segId
    end
    setsysvar("REC_IDX_" .. rid, idx)
end

function cleanRec()
    local rid = getsysvar("REC_SWEEP") or ""
    if rid == "" then return end
    local idx = getsysvar("REC_IDX_" .. rid) or ""
    local segId = idx:match("^(%d+)")
    if segId then
        setsysvar("REC_" .. rid .. "_" .. segId, "")
        setsysvar("REC_IDX_" .. rid, idx:sub(#segId + 2))
    else
        setsysvar("REC_IDX_" .. rid, "")
        setsysvar("REC_SWEEP", "")
    end
end