Add a configurable fakeAuth (StubAuth can't express the logged-out case)
and assert: /welcome renders the logged-out CTA with no session and the
logged-in controls with one, unauthenticated / redirects to /welcome,
unauthenticated deep links redirect to /auth/login, and an authenticated
root still renders the list.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
