Add cleanup message and option to keep temporary pcap file

- Show message when deleting temporary pcap file
- Add KEEP_PCAP environment variable option to keep the file for analysis
  Usage: KEEP_PCAP=1 sudo ./test_monitor_tshark.sh wlan0 36 10

Co-authored-by: Cursor <cursoragent@cursor.com>

test_monitor_tshark.sh

@@ -161,8 +161,13 @@ CAPTURE_OUTPUT=$(tshark -q -r "$TEMP_PCAP" -n -T fields \
     -e radiotap.present \
     2>/dev/null || true)
 
-# Clean up temp file
+# Clean up temp file (unless KEEP_PCAP is set)
+if [ -z "${KEEP_PCAP:-}" ]; then
+    echo "Cleaning up temporary pcap file: $TEMP_PCAP"
     rm -f "$TEMP_PCAP"
+else
+    echo "Keeping temporary pcap file: $TEMP_PCAP"
+fi
 
 # Force output flush
 sync