fix: add VAD config and audio relay logging for voice chat

- Add realtimeInputConfig with high sensitivity VAD to Gemini setup
- Log audio chunk flow and non-serverContent Gemini messages for debugging

Co-authored-by: Claude <noreply@anthropic.com>

Author: zcoderr

api/src/routes/voice/relay.ts

@@ -113,17 +113,36 @@ export class GeminiLiveRelay {
         systemInstruction: {
           parts: [{ text: this.session.systemInstruction }],
         },
+        realtimeInputConfig: {
+          automaticActivityDetection: {
+            disabled: false,
+            startOfSpeechSensitivity: 'START_SENSITIVITY_HIGH',
+            endOfSpeechSensitivity: 'END_SENSITIVITY_HIGH',
+            prefixPaddingMs: 20,
+            silenceDurationMs: 500,
+          },
+        },
       },
     };
     this.geminiWs?.send(JSON.stringify(setup));
   }
 
+  private clientChunkCount = 0;
+
   /** Handle messages from the client */
   private handleClientMessage(raw: WebSocket.Data): void {
     try {
       const msg = JSON.parse(raw.toString());
 
       if (msg.type === 'audio' && this.isSetupComplete) {
+        this.clientChunkCount++;
+        if (this.clientChunkCount === 1 || this.clientChunkCount % 100 === 0) {
+          logger.info('[voice-relay] audio chunk', {
+            n: this.clientChunkCount,
+            bytes: msg.data?.length ?? 0,
+            userId: this.session.userId,
+          });
+        }
         // Forward audio to Gemini in realtimeInput format
         this.geminiWs?.send(
           JSON.stringify({
@@ -157,7 +176,14 @@ export class GeminiLiveRelay {
       }
 
       const sc = msg.serverContent;
-      if (!sc) return;
+      if (!sc) {
+        // Log unexpected Gemini messages (errors, tool calls, etc.)
+        const keys = Object.keys(msg).join(',');
+        if (keys !== 'setupComplete') {
+          logger.info('[voice-relay] gemini non-serverContent msg', { keys });
+        }
+        return;
+      }
 
       // Forward audio data
       if (sc.modelTurn?.parts) {