open_term() launched sclang directly, bypassing parvagues-sc.service and its
10-pipewire-jack.conf drop-in. With jack2 installed, ldconfig hands scsynth the
real libjack, it finds no server and starts jackd on hw:sofsoundwire, which
takes the card from PipeWire by D-Bus reservation. Meters move, nothing is
audible (raw jackd -dalsa bypasses ALSA UCM, so the SOF speaker route is never
enabled), and Bluetooth cannot work at all since jackd has no BT backend.

Also adds tools/parvagues.desktop so the ordered launcher is one Super-key away;
nothing had ever been installed in ~/.local/share/applications.