Add swipe-down aux screen (SOCKTOP_AUX_CMD)

A separate tmux window running any TUI, reached with a vertical swipe from
any carousel screen; swiping up returns to the exact window/zoom you left.
The aux window is excluded from the horizontal carousel and horizontal
swipes on it are inert. Bound only when SOCKTOP_AUX_CMD is set.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

socktop-gestures

@@ -20,6 +20,9 @@ done
 : "${FINGER_COUNTS:=1 2 3}"
 : "${GESTURE_IN:=RL}"
 : "${GESTURE_OUT:=LR}"
+: "${SOCKTOP_AUX_CMD:=}"
+: "${GESTURE_AUX_IN:=UD}"
+: "${GESTURE_AUX_OUT:=DU}"
 
 SWIPE_CMD=${SWIPE_CMD:-$(dirname "$0")/socktop-swipe}
 [ -x /usr/local/bin/socktop-swipe ] && SWIPE_CMD=/usr/local/bin/socktop-swipe
@@ -83,6 +86,10 @@ set --
 for f in $FINGER_COUNTS; do
 	set -- "$@" -g "$f,$GESTURE_IN,*,*,R,$SWIPE_CMD next"
 	set -- "$@" -g "$f,$GESTURE_OUT,*,*,R,$SWIPE_CMD prev"
+	if [ -n "$SOCKTOP_AUX_CMD" ]; then
+		set -- "$@" -g "$f,$GESTURE_AUX_IN,*,*,R,$SWIPE_CMD down"
+		set -- "$@" -g "$f,$GESTURE_AUX_OUT,*,*,R,$SWIPE_CMD up"
+	fi
 done
 
 exec lisgd $verbose \