Feature: exit to current directory

When `diskonaut` exits, it returns the user to the folder they were in when they started.

It would be nice if instead of doing that, it would change the user's working directory to the directory they are currently in with diskonaut.

Start by inspecting diskonaut's CLI entry point and how it exits after navigation. Determine whether the requested directory change can be exposed through the surrounding shell invocation, then verify that exiting leaves the shell in the directory currently selected in diskonaut rather than the original directory.

Written by the indexing model from the issue text.