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/components/navigation/SkipToContent.tsx

@@ -0,0 +1,14 @@
+import header from "../../../messages/en/components/header.json";
+import { MAIN_CONTENT_ID } from "../../../lib/mainContent";
+
+/**
+ * First focusable control in the shell. Revealed on focus so keyboard users
+ * can bypass the header and land on the group `<main>`.
+ */
+export default function SkipToContent() {
+  return (
+    <a href={`#${MAIN_CONTENT_ID}`} className="skip-to-content text-medium-label">
+      {header.skipToContent}
+    </a>
+  );
+}