Replace LiveKit with WebSocket Opus audio relay (#326)

desktop/public/worklet.js

@@ -1,19 +1,24 @@
 // AudioWorklet processor — runs in the AudioWorklet thread.
-// Accumulates PCM Float32 samples and sends 100ms batches to the main thread.
+// Accumulates PCM Float32 samples and sends 20ms batches to the main thread.
+//
+// ASSUMPTION: AudioContext runs at 48 kHz (Tauri WebView default on desktop).
+// The 960-sample buffer = exactly one 20ms Opus frame at 48 kHz. If the
+// sample rate differs (e.g. 44.1 kHz), frames will be slightly misaligned
+// with the Opus encoder. getUserMedia should request sampleRate: 48000.
 //
 // Supports push-to-talk (PTT) gating: when `this.transmitting` is false,
 // incoming audio frames are discarded and the buffer is reset. The main thread
 // sends `{ type: 'ptt', active: boolean }` messages to toggle transmission.
 // Default: transmitting=true (open mic for VAD mode compatibility).
 //
-// Note: when the worklet is disconnected, any partial buffer (< 4800 samples)
-// is silently dropped. The last ~100ms of speech may be lost on huddle leave.
+// Note: when the worklet is disconnected, any partial buffer (< 960 samples)
+// is silently dropped. The last ~20ms of speech may be lost on huddle leave.
 // This is acceptable for voice — losing a partial syllable at disconnect is
 // imperceptible compared to the natural end-of-conversation flow.
 class SttTapProcessor extends AudioWorkletProcessor {
   constructor() {
     super();
-    this.buffer = new Float32Array(4800); // ~100ms at 48kHz
+    this.buffer = new Float32Array(960); // ~20ms at 48kHz
     this.offset = 0;
     this.transmitting = true; // default: open (VAD mode). PTT mode sets false on init.
 
@@ -48,7 +53,7 @@ class SttTapProcessor extends AudioWorkletProcessor {
     if (this.offset >= this.buffer.length) {
       // Transfer ownership for zero-copy
       this.port.postMessage(this.buffer, [this.buffer.buffer]);
-      this.buffer = new Float32Array(4800);
+      this.buffer = new Float32Array(960);
       this.offset = 0;
 
       // Handle leftover samples