Fix duplicate CAVA instances via lockfile

pkill pattern was wrong (path has dancingcharacter not skeledance).
Now uses a lockfile to prevent QML from spawning multiple instances.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugin/contents/ui/cava-start.sh

@@ -1,6 +1,15 @@
 #!/usr/bin/env bash
-pkill -f "cava -p.*skeledance" 2>/dev/null
-pkill -f "cava-server.py"      2>/dev/null
+LOCK=/tmp/skeledance_cava.lock
+
+# Prevent multiple instances
+if [ -f "$LOCK" ] && kill -0 "$(cat "$LOCK")" 2>/dev/null; then
+  exit 0
+fi
+echo $$ > "$LOCK"
+trap 'rm -f "$LOCK"' EXIT
+
+pkill -x cava          2>/dev/null
+pkill -f cava-server   2>/dev/null
 sleep 0.2
 
 DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"