feat(app): UDS bridge (channel/invoke/emit) + xterm.js terminal, M0 e2e works

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/main.tsx

@@ -1,10 +1,10 @@
 import React from "react";
 import ReactDOM from "react-dom/client";
+import { App } from "./App";
+import "@xterm/xterm/css/xterm.css";
 
 ReactDOM.createRoot(document.getElementById("root")!).render(
   <React.StrictMode>
-    <div style={{ color: "#ddd", fontFamily: "monospace", padding: 16 }}>
-      spacesh — scaffold OK
-    </div>
+    <App />
   </React.StrictMode>
 );