fix: start VAD gate open to avoid permanent silence on model load failure

Starting the gate closed caused permanent silence if the ONNX model or
WASM files failed to load (onFrameProcessed never fired). Gate now starts
open so audio flows immediately; the first silence frame closes it. Also
ensures the gate is always reset to open when VAD is disabled.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/livekit/SileroVADGate.ts

@@ -82,9 +82,10 @@ export class SileroVADGate {
       onSpeechRealStart: (): void => {},
     });
 
-    // Gate starts closed — audio is muted until the first speech frame arrives.
-    this.gateOpen = false;
-    this.onClose();
+    // Gate starts OPEN so audio flows immediately. The first silence frame
+    // will close it. This also means a failed model load degrades gracefully
+    // (audio still flows) rather than permanently muting the user.
+    this.gateOpen = true;
 
     await this.vad.start();
     log.info("MicVAD started");

src/state/CallViewModel/localMember/Publisher.ts

@@ -454,7 +454,7 @@ export class Publisher {
         void vadGate.destroy();
         vadGate = null;
       }
-      // Reset gate to open so audio flows if VAD is toggled off mid-call
+      // Always reopen gate when VAD stops so audio flows without VAD
       transformer?.setVADOpen(true);
     };
 
@@ -468,8 +468,6 @@ export class Publisher {
       }
       const stream = new MediaStream([rawTrack]);
       vadGate = new SileroVADGate(stream, ctx);
-      // Close the gate immediately — VAD will open it once speech is confirmed.
-      transformer?.setVADOpen(false);
       vadGate.onOpen  = (): void => transformer?.setVADOpen(true);
       vadGate.onClose = (): void => transformer?.setVADOpen(false);
       vadGate.start().catch((e: unknown) => {