docs: rewrite Guest-Mode page, fix Local-Development reference Guest-Mode.md: full rewrite to reflect automatic guest mode — isGuest is now a derived value (!user && !loading), no localStorage flag, no opt-in buttons, GuestBanner has no Exit button, middleware returns 401 JSON not redirect. Local-Development.md: remove stale 'Explore as Guest' button reference. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
docs: comprehensive technical wiki — architecture, API reference, auth & security, design system, guest mode, local dev