chore: import upstream snapshot with attribution

examples/react/frontend/src/App.tsx

@@ -0,0 +1,21 @@
+import { useEffect, useState } from "react";
+
+export default function App() {
+  const [bridge, setBridge] = useState("checking...");
+
+  useEffect(() => {
+    setBridge((window as any).zero ? "available" : "not enabled");
+  }, []);
+
+  return (
+    <main>
+      <p className="eyebrow">Native SDK + React</p>
+      <h1>React</h1>
+      <p className="lede">A React frontend running inside the system WebView.</p>
+      <div className="card">
+        <span>Native bridge</span>
+        <strong>{bridge}</strong>
+      </div>
+    </main>
+  );
+}

examples/react/frontend/src/index.css

@@ -0,0 +1,52 @@
+:root {
+  color: #0f172a;
+  background: #f8fafc;
+  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
+}
+
+body {
+  min-width: 320px;
+  min-height: 100vh;
+  margin: 0;
+  display: grid;
+  place-items: center;
+}
+
+main {
+  width: min(560px, calc(100vw - 48px));
+  padding: 32px;
+  border-radius: 24px;
+  background: white;
+  box-shadow: 0 24px 60px rgba(15, 23, 42, 0.14);
+}
+
+h1 {
+  margin: 0 0 12px;
+  font-size: clamp(2rem, 8vw, 4rem);
+  line-height: 1;
+}
+
+.eyebrow {
+  margin: 0 0 12px;
+  color: #2563eb;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  text-transform: uppercase;
+}
+
+.lede {
+  margin: 0 0 24px;
+  color: #475569;
+  line-height: 1.6;
+}
+
+.card {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 16px;
+  padding: 16px;
+  border: 1px solid #e2e8f0;
+  border-radius: 16px;
+  background: #f8fafc;
+}

examples/react/frontend/src/main.tsx

@@ -0,0 +1,10 @@
+import { StrictMode } from "react";
+import { createRoot } from "react-dom/client";
+import App from "./App";
+import "./index.css";
+
+createRoot(document.getElementById("root")!).render(
+  <StrictMode>
+    <App />
+  </StrictMode>
+);