Fix regression: use temp file for tshark output parsing

- Write tshark output to temp file first to avoid pipe issues
- Redirect stderr to /dev/null to suppress field errors
- Filter to only keep lines starting with frame numbers
- This should fix the issue where only 1 packet was parsed instead of 217

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

test_monitor_tshark.sh

@@ -196,7 +196,9 @@ fi
 # Now parse the pcap file to extract fields
 # Only extract 802.11 header fields - data payloads are encrypted
 # Include PHY rate and MCS for histograms
-CAPTURE_OUTPUT=$(tshark -q -r "$TEMP_PCAP" -n -T fields \
+# Extract to temp file first to avoid pipe issues, then filter
+TEMP_TSHARK_OUTPUT=$(mktemp /tmp/tshark_output_XXXXXX.txt)
+tshark -q -r "$TEMP_PCAP" -n -T fields \
     -e frame.number \
     -e frame.time \
     -e wlan.ra \
@@ -212,7 +214,11 @@ CAPTURE_OUTPUT=$(tshark -q -r "$TEMP_PCAP" -n -T fields \
     -e radiotap.mcs.index \
     -e wlan_radio.data_rate \
     -e wlan_radio.mcs.index \
-    2>&1 | grep -v "^tshark:" | grep -v "^Running as" | grep -v "^Capturing" || true)
+    2>/dev/null > "$TEMP_TSHARK_OUTPUT" || true
+
+# Filter out non-packet lines (keep only lines starting with frame numbers)
+CAPTURE_OUTPUT=$(grep -E '^[0-9]+\t' "$TEMP_TSHARK_OUTPUT" || true)
+rm -f "$TEMP_TSHARK_OUTPUT"
 
 # Clean up temp file (unless KEEP_PCAP is set)
 if [ -z "$KEEP_PCAP" ]; then