Initial commit: swipe-to-zoom touchscreen navigation for socktop

Tiled socktop dashboard where a right-to-left swipe zooms into each host
full-screen and left-to-right walks back out.

The carousel is tmux pane zoom rather than separate socktop instances, so
there is one process per host: half the processes, no reconnect delay when
swiping back, and constant polling load on the monitored hosts.

Gestures come from lisgd because libinput emits gesture events only for
touchpads, never touchscreens, which rules out libinput-gestures entirely.

Documents the four gotchas found while building this: panels reporting 2-3
contacts for a one-finger swipe, X needing to ignore the panel so the
terminal and socktop stop competing for the same touches, tmux mouse mode
being incompatible with swipes, and lisgd not grabbing the device
exclusively so two instances double-fire.

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

tools/diag.sh

@@ -0,0 +1,56 @@
+#!/bin/sh
+# Gesture diagnostic. Two stages, each answering exactly one question.
+#
+# Stage 1: is the panel delivering events to us at all?
+# Stage 2: which direction and how many contacts does lisgd see?
+#
+# Stage 2 is the important one. Each line reads:
+#     [swipe]: Cfg(f=1/s=3/e=0/d=0) <=> Evt(f=2/s=3/e=1/d=2)
+#              ^ what you configured    ^ what actually happened
+# f=fingers, s=direction, e=edge, d=distance. Direction enum:
+#     0=DU (down-to-up)  1=UD  2=LR (left-to-right)  3=RL (right-to-left)
+#
+# If Cfg and Evt agree on s= but differ on f=, your panel reports more contacts
+# than you configured -- add them to FINGER_COUNTS in the config.
+set -eu
+
+for c in /usr/local/etc/socktop-swipe.env "$(dirname "$0")/../config.env"; do
+	[ -r "$c" ] && . "$c" && break
+done
+: "${TOUCH_DEV:?no TOUCH_DEV configured}"
+: "${SCREEN_W:=1024}"
+: "${SCREEN_H:=600}"
+: "${SWIPE_THRESHOLD:=80}"
+: "${SWIPE_LENIENCY:=30}"
+
+echo "=============================================================="
+echo "STAGE 1 -- is the panel delivering events at all?"
+echo "Touch and drag on the TOUCHSCREEN for the next 6 seconds..."
+echo "=============================================================="
+bytes=$(timeout 6 cat "$TOUCH_DEV" 2>/dev/null | wc -c)
+echo
+echo "  read $bytes bytes from $TOUCH_DEV"
+if [ "$bytes" -eq 0 ]; then
+	cat <<-EOF
+	  -> NOTHING. Stage 2 cannot work. Check, in order:
+	     * are you in the 'input' group? (id -nG | grep input; needs a relogin)
+	     * is TOUCH_DEV the right device? (tools/find-device.sh)
+	EOF
+	exit 1
+fi
+echo "  -> device is live."
+echo
+
+echo "=============================================================="
+echo "STAGE 2 -- what does lisgd actually see?"
+echo "All four directions are bound, for 1, 2 and 3 contacts."
+echo "Swipe LEFT, RIGHT, UP, DOWN. Ctrl-C when done."
+echo "=============================================================="
+set --
+for f in 1 2 3; do
+	for g in RL LR DU UD; do
+		set -- "$@" -g "$f,$g,*,*,R,echo \"  >>> FIRED: ${f}-contact $g\""
+	done
+done
+exec lisgd -v -d "$TOUCH_DEV" -w "$SCREEN_W" -h "$SCREEN_H" \
+	-t "$SWIPE_THRESHOLD" -r "$SWIPE_LENIENCY" "$@"