A GUI-launched Ardour has a BARE argv (only gig-up passes the session as an
argument), so argv-matching alone left the files lens blind on the real rig.
Resolution now climbs: argv → /proc/<pid>/cwd holding a *.ardour → open-fd
symlink targets (most-fds wins on ambiguity, logged once). Injectable proc_root
makes each rung testable against a fake /proc; 9 new tests reproduce the exact
live gap (163 green). check-mix.py shares the latent argv-only bug — flagged in
the sync comment, not fixed this pass.
