feat: initial fate based SPA

app/spa/router.tsx

@@ -0,0 +1,69 @@
+import { Link, Outlet, createRootRoute, createRoute, createRouter } from "@tanstack/react-router";
+
+const rootRoute = createRootRoute({
+  component: RootLayout,
+});
+
+const indexRoute = createRoute({
+  getParentRoute: () => rootRoute,
+  path: "/",
+  component: HomePage,
+});
+
+const machinesRoute = createRoute({
+  getParentRoute: () => rootRoute,
+  path: "/machines",
+  component: MachinesPage,
+});
+
+const routeTree = rootRoute.addChildren([indexRoute, machinesRoute]);
+
+export const router = createRouter({
+  basepath: __PREFIX__,
+  routeTree,
+});
+
+declare module "@tanstack/react-router" {
+  interface Register {
+    router: typeof router;
+  }
+}
+
+function RootLayout() {
+  return (
+    <div className="min-h-screen bg-neutral-950 text-white">
+      <header className="border-b border-white/10 px-6 py-4">
+        <nav className="flex gap-4 text-sm">
+          <Link to="/">Home</Link>
+          <Link to="/machines">Machines</Link>
+        </nav>
+      </header>
+
+      <main className="p-6">
+        <Outlet />
+      </main>
+    </div>
+  );
+}
+
+function HomePage() {
+  return (
+    <section className="space-y-2">
+      <h1 className="text-2xl font-semibold">Headplane SPA</h1>
+      <p className="text-neutral-400">
+        This is the one-way SPA shell. Data should move to raw Fate views and actions.
+      </p>
+    </section>
+  );
+}
+
+function MachinesPage() {
+  return (
+    <section className="space-y-2">
+      <h1 className="text-2xl font-semibold">Machines</h1>
+      <p className="text-neutral-400">
+        First migration target: replace the React Router loader/action/SSE model with raw Fate.
+      </p>
+    </section>
+  );
+}