Pause playback while transmitting and declare microphone use.

macOS refuses capture without a usage string, and queued remote audio was still handed to the speaker after push-to-talk began.

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

app.go

@@ -23,7 +23,7 @@ func (a *App) startup(ctx context.Context) {
 		a.station.Fail("could not open the audio device")
 		return
 	}
-	go func() { _ = a.station.Run(runCtx) }()
+	go func() { _ = a.station.Run(runCtx) }() // Run returns when the window closes.
 }
 
 func (a *App) shutdown(context.Context) {