Very nice! If you made it a WindowCommand, rather than a TextCommand, then it'd work in panes that don't have any files. Currently, if you create a pane, and then focus it immediately, you aren't able to move back.
On the nitpicky side of things, there's a few print statements still in the code, and your readme still mentions the old name
Edit: Apparently I'm foolish, and was looking at the wrong repo