Run Piper ONNX in a module worker

piper-runtime.js

@@ -6,7 +6,9 @@ const pending = new Map();
 
 function getWorker() {
   if (worker) return worker;
-  worker = new Worker(workerUrl);
+  // ONNX Runtime resolves its WASM loader relative to the worker module URL.
+  // Keep the worker as ESM so import.meta.url remains available at runtime.
+  worker = new Worker(workerUrl, {type: 'module'});
   worker.onmessage = event => {
     const message = event.data || {};
     const request = pending.get(message.id);