feat(frontend): 4-zone shell + F1 loop end-to-end (MSW)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.test.tsx

@@ -1,7 +1,7 @@
 import { render, screen } from "@testing-library/react";
 import { App } from "./App";
 
-test("App renders the ThothII title", () => {
+test("App renders the shell with create affordance", () => {
   render(<App />);
-  expect(screen.getByText(/ThothII/i)).toBeInTheDocument();
+  expect(screen.getByRole("button", { name: /nuova/i })).toBeInTheDocument();
 });