Give the shell one header, a skip link, and a cookie-aware first paint.

Breakpoint clones were still in the tab order, marketing always painted Log in, and at 430px the logo overlay covered Use cases and Learn.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/layout.tsx

@@ -6,10 +6,9 @@ import { ASSETS, getAssetPath } from "../lib/assetUtils";
 import { PRODUCTION_SITE_ORIGIN } from "../lib/siteMetadata";
 import "./globals.css";
 
-// `force-dynamic` is now scoped to `(app)/layout.tsx` and `(admin)/layout.tsx`
-// (the only groups that read the session via `ConditionalNavigation`). Marketing
-// renders a client-side `MarketingNavigation` so its HTML can be statically
-// optimized — TTFB drops to CDN speed for guests.
+// Session chrome (`ConditionalNavigation`) lives in `(marketing)`, `(app)`, and
+// `(admin)` layouts, behind `<Suspense>`, so the static shell can prerender while
+// the header streams with the request cookie.
 //
 // MessagesProvider + AuthModalProvider are mounted per route group (Phase 4b):
 // `(marketing)` gets a trimmed slice without `create.*` (~41 KB gzipped saved