feat: Unleash feature flags via src/lib/flags.tsx, hello-banner on home page

src/test-setup.ts

@@ -1 +1,6 @@
 import "@testing-library/jest-dom/vitest";
+import { cleanup } from "@testing-library/react";
+import { afterEach } from "vitest";
+
+// vitest globals are off, so Testing Library can't register this itself.
+afterEach(cleanup);