archive: 在 Windows 上重命名更改目录还会默默地回滚 spec 写入

openspec archive fails on Windows with EPERM when renaming the change directory. This looks like a regression of #197, which was closed as completed, and it now has a worse consequence than that report described: the spec write is rolled back with it, and the empty directory it leaves behind is invisible to git.

Reproduced twice in a row, on two different changes, in the same repository.