add a tone test mode that bypasses the soundcard

Add -tone-test to transmit a generated 440 Hz Opus tone and save
incoming audio to the file named by -tone-out.
Diagnosing an audio problem previously required a working capture and
playback device, which is exactly what is in question. This mode opens
no OpenAL device at all, so the network and codec path can be tested
on a machine with no sound hardware.

Open the capture file before starting the generator.
Starting transmission first left a tone goroutine running with nowhere
to write when the path was unusable.

Refuse file playback while in tone test mode, and ignore the
microphone volume keys.
Both operate on a stream that does not exist here.

Stop the generator and detach the file saver on disconnect.
A reconnect otherwise attached a second saver to the same file.

Add -auto-transmit to key the microphone as soon as the connection is
up.
Useful for a bot or a monitoring client that should never need a
keypress. It runs from both the connect event and the point where the
audio stream is created, because the server's welcome arrives before
the stream exists.

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

barnard.go

@@ -27,9 +27,10 @@ type Barnard struct {
 	Address   string
 	TLSConfig tls.Config
 
-	Stream    *gumbleopenal.Stream
-	Tx        bool
-	Connected bool
+	Stream       *gumbleopenal.Stream
+	Tx           bool
+	AutoTransmit bool // auto-start transmission on connect
+	Connected    bool
 
 	Ui              *uiterm.Ui
 	UiOutput        uiterm.Textview
@@ -62,6 +63,13 @@ type Barnard struct {
 	FileStream      *fileplayback.Player
 	FileStreamMutex sync.Mutex
 
+	// Added for tone test mode (bypasses all soundcard/OpenAL)
+	ToneTest            bool
+	ToneTestOutput      string
+	toneTestStop        chan struct{}
+	toneTestSaver       *AudioFileSaver
+	toneTestSaverDetach gumble.Detacher
+
 	// Added for recording
 	RecordingMutex    sync.Mutex
 	Recorder          *recording.Recorder
@@ -74,6 +82,17 @@ type Barnard struct {
 	adminACL           *gumble.ACL
 }
 
+func (b *Barnard) cleanupToneTestAudio() {
+	if b.toneTestSaverDetach != nil {
+		b.toneTestSaverDetach.Detach()
+		b.toneTestSaverDetach = nil
+	}
+	if b.toneTestSaver != nil {
+		b.toneTestSaver.Stop()
+		b.toneTestSaver = nil
+	}
+}
+
 func (b *Barnard) StopTransmission() {
 	if b.Tx {
 		b.Notify("micdown", "me", "")