You can do a `jj new; jj restore --restore-descendants -f commit_id -t @-` with a commit id (not change id!) from the evolog to "inject" a snapshot from the evolog below your current @, leaving the file state at @ (and everywhere else in the log) intact.
Or if you have a commit ID (or otherwise revset; so a "main@origin" or whatever would work) of a specific commit that you want already, can use that instead of course too.
