Add hello-snapshot UIWorker example

Smallest UIWorker demo: a voice LLM in the main pipeline delegates
screen-relevant utterances to a UIWorker via a respond job; the UIWorker
auto-injects the current <ui_state> and answers grounded in what's on screen.
Includes a vanilla-JS client that streams accessibility snapshots over RTVI.

examples/multi-worker/ui-worker/hello-snapshot/client/vite.config.js

@@ -0,0 +1,7 @@
+import { defineConfig } from "vite";
+
+export default defineConfig({
+  server: {
+    port: 5173,
+  },
+});