The serving process built its arguments by hand, so in daemon mode
--shared-dir stayed on the attached run, where shares belong to the
daemon and the flag is ignored. The daemon fell back to sharing its
default folder - which on a developer machine contains the probe files
earlier buggy runs deposited, so the test only passed by finding
served.bin in leftovers. args_with routes the share to the process
whose session does the sharing in either mode.