fix: copy Silero VAD model out of asar so native code can read it

The bundled silero_vad.onnx lives inside Electron's app.asar which
native C++ (sherpa-onnx) cannot open via OS file I/O. On first voice
activation, copy the model to ~/.paseo/models/local-speech/silero-vad/
using Node.js fs (asar-aware) and point the native code there.

packages/server/src/server/speech/providers/local/runtime.ts

@@ -22,7 +22,7 @@ import { SherpaParakeetRealtimeTranscriptionSession } from "./sherpa/sherpa-para
 import { SherpaRealtimeTranscriptionSession } from "./sherpa/sherpa-realtime-session.js";
 import { SherpaOnnxSTT } from "./sherpa/sherpa-stt.js";
 import { SherpaOnnxTTS } from "./sherpa/sherpa-tts.js";
-import { SherpaSileroTurnDetectionProvider } from "./sherpa/silero-vad-provider.js";
+import { ensureSileroVadModel, SherpaSileroTurnDetectionProvider } from "./sherpa/silero-vad-provider.js";
 
 type LocalSttEngine =
   | { kind: "offline"; engine: SherpaOfflineRecognizerEngine }
@@ -236,7 +236,15 @@ export async function initializeLocalSpeechServices(params: {
     providers.voiceTurnDetection.enabled !== false &&
     providers.voiceTurnDetection.provider === "local"
   ) {
-    turnDetectionService = new SherpaSileroTurnDetectionProvider({}, logger);
+    let vadModelPath: string | undefined;
+    if (localConfig) {
+      try {
+        vadModelPath = await ensureSileroVadModel(localConfig.modelsDir, logger);
+      } catch (err) {
+        logger.warn({ err }, "Failed to provision Silero VAD model, falling back to bundled");
+      }
+    }
+    turnDetectionService = new SherpaSileroTurnDetectionProvider({ modelPath: vadModelPath }, logger);
   }
 
   if (providers.voiceStt.enabled !== false && providers.voiceStt.provider === "local") {

packages/server/src/server/speech/providers/local/sherpa/silero-vad-provider.ts

@@ -1,10 +1,43 @@
+import { copyFile, mkdir, stat } from "node:fs/promises";
+import path from "node:path";
+
 import type { Logger } from "pino";
 
 import type {
   TurnDetectionProvider,
   TurnDetectionSession,
 } from "../../../turn-detection-provider.js";
-import { SherpaSileroVadSession, type SherpaSileroVadSessionConfig } from "./silero-vad-session.js";
+import {
+  resolveBundledSileroVadModelPath,
+  SherpaSileroVadSession,
+  type SherpaSileroVadSessionConfig,
+} from "./silero-vad-session.js";
+
+const SILERO_VAD_DIR = "silero-vad";
+const SILERO_VAD_FILE = "silero_vad.onnx";
+
+/**
+ * Ensure the Silero VAD ONNX model exists in modelsDir where native code can
+ * read it. The bundled asset lives inside Electron's app.asar which native C++
+ * cannot open, so we copy it out on first run using Node.js fs (asar-aware).
+ */
+export async function ensureSileroVadModel(modelsDir: string, logger: Logger): Promise<string> {
+  const destDir = path.join(modelsDir, SILERO_VAD_DIR);
+  const destPath = path.join(destDir, SILERO_VAD_FILE);
+
+  try {
+    const s = await stat(destPath);
+    if (s.isFile() && s.size > 0) return destPath;
+  } catch {
+    // not present yet
+  }
+
+  const bundledPath = resolveBundledSileroVadModelPath();
+  await mkdir(destDir, { recursive: true });
+  await copyFile(bundledPath, destPath);
+  logger.info({ destPath }, "Copied Silero VAD model to models directory");
+  return destPath;
+}
 
 export class SherpaSileroTurnDetectionProvider implements TurnDetectionProvider {
   public readonly id = "local" as const;

packages/server/src/server/speech/providers/local/sherpa/silero-vad-session.ts

@@ -34,7 +34,7 @@ type SherpaVadModule = {
   CircularBuffer: new (capacity: number) => SherpaCircularBufferHandle;
 };
 
-function resolveBundledSileroVadModelPath(): string {
+export function resolveBundledSileroVadModelPath(): string {
   return fileURLToPath(new URL("./assets/silero_vad.onnx", import.meta.url));
 }