v3.9.1: plain/WASAPI streams now play on an ASIO-mode receiver (silent-mic fix)

Receiver: a Mixed (plain) session is rendered on an active lane in BothIndependent mode instead of being skipped, so a WASAPI-only sender is no longer silent to a receiver that has an ASIO driver selected. Also port the per-session buffer depth-drain (stops the receive jitter buffer bloating).

Sender: add sndAudFr meter (audio frames actually sent) to localise capture vs send.

App: startup sound cue (machine-wide, Preferences); stop sending audio when no peer is reachable (issue #8). Version 3.9.1.

Server (relay): fix updater version-compare for multi-dot tags, guard the main loop against crashes, reject spoofed BYE from a mismatched endpoint.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.Sender/AudioSender.cs

@@ -188,6 +188,15 @@ public sealed class AudioSender : IDisposable
         return a > b ? a : b;
     }
 
+    /// <summary>Total audio frames both lanes actually handed to the wire since the last call
+    /// (resets on read). Pairs with <see cref="TakeMaxSenderPreEncodePeak"/> on the diag line:
+    /// capPeak proves real signal reached the encoder; this proves frames left the socket. A
+    /// high capPeak with zero frames sent localises a silence to the encode/encrypt stage — the
+    /// missing measurement behind the "mic only works in ASIO" report. In WasapiOnly mode only
+    /// defaultLane fires, so this number IS the WASAPI mic lane's output.</summary>
+    public long TakeSenderAudioFramesSent() =>
+        defaultLane.TakeAudioFramesSent() + asioLane.TakeAudioFramesSent();
+
     // Cross-buffer (boundary) and within-buffer (content) split — see AudioStepProbe for the
     // diagnostic distinction. Used by the per-second diag logger to emit two extra columns so
     // an offline log inspection can tell a real audio transient apart from a buffer-boundary