fix(gig): gig-up.sh crashed on launch — open_term read an unused $1 under set -u

First real end-to-end run of the ordered launcher aborted immediately at
"starting SuperDirt": open_term() carried a vestigial `local cmd="$1"`
(the sclang command is hardcoded inside the function), but the function is
called with no arguments, so `set -u` turned the unused positional into a
fatal 'unbound variable' before sclang ever spawned.

Dropped the dead parameter. Re-ran: SuperDirt boots headless, claims the
LaunchControl XL (aconnect 16:0 -> SuperCollider 128:3) BEFORE Ardour opens,
then Ardour 9.2.0 (Tidal Multi) + Pulsar come up — the whole rig from one
command, no disconnect/reconnect MIDI dance. Task #9 validated live.

gig-up.sh

@@ -40,8 +40,8 @@ pick_term(){
   echo ""
 }
 
-open_term(){  # open_term "<shell command>" — run cmd in a new terminal window
-  local term; term="$(pick_term)"; local cmd="$1"
+open_term(){  # open a new terminal running the headless sclang gig-boot
+  local term; term="$(pick_term)"
   if [ -z "$term" ]; then
     warn "no terminal emulator found — running SuperDirt in the background (post → $DIR/gig-sclang.log)"
     ( cd "$DIR" && QT_QPA_PLATFORM=offscreen setsid sclang gig-boot.scd >gig-sclang.log 2>&1 & )