升级之后再降级 dsh

undohaven restore --to <pre-upgrade-snapshot>。旧程序读不了新的存储版本戳。先恢复升级前快照，再安装旧版本。云端跨大版本回退是专业版。本机快照仍可离线恢复。

undohaven restore --to <pre-upgrade-snapshot>. A storage version stamp cannot be read by the older build. Restore the pre-upgrade snapshot, then install the older package. Crossing a major line (0.2 to 0.3, or 1 to 2) on a cloud snapshot is a Pro feature. A local snapshot can still be restored offline.