fix(web): hero Get Started CTA -> /docs#installation (closes #3848)

Get Started button previously linked to /docs (root), landing users on
Overview. Issue #3848 reporter and concurrent PR #3948 asked for a
deeper link straight to Installation.

lib/docs-sections.ts declares 'installation' as a stable section id
rendered via <section id={section.id}> in app/[locale]/docs/page.tsx,
so /docs#installation is a valid deep link.

This also supersedes the in-flight PR #3948 (which targets the
pre-decomposition landing-page.tsx).

packages/web/components/landing/sections/hero.tsx

@@ -72,7 +72,7 @@ export async function HeroSection(): Promise<JSX.Element> {
         </div>
 
         <div className="flex flex-col gap-4 sm:flex-row">
-          <Link href="/docs">
+          <Link href="/docs#installation">
             <Button
               size="lg"
               className="h-12 bg-cyan-500 px-8 text-lg font-bold text-black shadow-sm hover:bg-cyan-600"