Add async-tasks UIWorker example

A UIWorker with a custom reply tool fans research out to three BaseWorker peers
via start_user_job_group; their progress streams to the client as ui-task cards
and the user can cancel a group mid-flight.

examples/multi-worker/ui-worker/async-tasks/client/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "async-tasks-client",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "@pipecat-ai/client-js": "1.9.0",
+    "@pipecat-ai/small-webrtc-transport": "^1.10.2"
+  },
+  "devDependencies": {
+    "vite": "^8"
+  }
+}