[CHORE] improve recursive listing error msg

[avriiil]

This adds a more descriptive error message to the glob_scan to direct users towards recursive listing capabilities

Closes #2109

[jaychia]

Nice! The error message should also be {}/**, since in our globbing syntax the ** must be a standalone "fragment". I think we should be able to do this by stripping the right-most / in glob_path and then adding / in the error string!

[avriiil]

@jaychia - my rust is not great, but this seems to do the trick. lmk what you think

[jaychia]

Nice!