Use single-thread ONNX runtime for mobile speech

piper-worker.js

@@ -1,7 +1,8 @@
 import {TtsSession} from '@mintplex-labs/piper-tts-web';
+import * as onnxRuntime from 'onnxruntime-web';
 import {trackDownloadProgress} from './piper-download-progress.mjs';
 import {localPiperModelUrl} from './piper-model-routing.mjs';
-import {createOnnxWasmPaths} from './piper-onnx-config.mjs';
+import {configureOnnxRuntime, createOnnxWasmPaths} from './piper-onnx-config.mjs';
 
 const VOICE_ID = 'sv_SE-nst-medium';
 const ASSET_ROOT = '/static/piper-wasm-v1';
@@ -50,6 +51,7 @@ let activeRequestId = null;
 
 async function getSession() {
   if (!sessionPromise) {
+    configureOnnxRuntime(onnxRuntime);
     sessionPromise = TtsSession.create({
       voiceId: VOICE_ID,
       wasmPaths: {