docs(site): section 00's heading names the idea itself

The h2 is now the deck's thesis title, "An ontology written clearly
enough runs directly", in place of the essay's section heading "Why
code recedes", which reads without context to a visitor who has not
opened the essay yet.

Claude-Session: https://claude.ai/code/session_011hRnra93sK5Q2gTYYTbdJR
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

apps/docs/app/[lang]/page.tsx

@@ -331,7 +331,7 @@ export default function HomePage() {
             </span>
           </div>
           <h2 className="mt-4 max-w-2xl text-3xl font-bold tracking-tight md:text-4xl" style={{ fontFamily: 'var(--l-display)' }}>
-            Why code recedes
+            An ontology written clearly enough runs directly
           </h2>
           {/* The figure's caption takes its spacing and colour from the blog's prose
               styles there; this page has no prose wrapper, so the wrapper sets them. */}