Add -tcp flag to disable UDP and force audio through TCP tunnel

Adds Config.DisableUDP field. When set:
- DialWithDialer skips startUDP() entirely (no UDP socket, no UDP reader)
- WriteAudio skips WriteAudioUDP and goes straight to TCP-tunneled audio

Useful for debugging crypto/transport issues — rules out UDP-specific
problems like NAT, firewall, or OCB2 counter mismatches.

main.go

@@ -119,6 +119,7 @@ func main() {
 	autoTransmit := flag.Bool("auto-transmit", false, "start transmitting immediately on connect")
 	toneTest := flag.Bool("tone-test", false, "send a 440 Hz test tone instead of microphone (bypasses soundcard)")
 	toneTestOutput := flag.String("tone-out", "incoming.pcm", "file to save incoming audio to in tone-test mode")
+	tcpOnly := flag.Bool("tcp", false, "disable UDP, force audio through TCP tunnel")
 	logLevel := flag.String("log", "warn", "log level: debug, info, warn, error")
 	logFile := flag.String("logfile", "", "write logs to this file (in addition to stderr)")
 
@@ -218,6 +219,7 @@ func main() {
 		NoiseSuppressor: noise.NewSuppressor(),
 	}
 	b.Config.Buffers = *buffers
+	b.Config.DisableUDP = *tcpOnly
 
 	b.Hotkeys = b.UserConfig.GetHotkeys()
 	b.UserConfig.SaveConfig()