fix: use youtube-nocookie.com embed to avoid bot detection page

Switch YouTube embed URL to privacy-enhanced domain to prevent
Google's bot detection page from loading inside the iframe.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: stephanj

docusaurus/src/pages/index.js

@@ -74,7 +74,7 @@ export default function Home() {
               <div className={styles.videoContainer}>
                 <iframe
                   className={styles.demoVideo}
-                  src="https://www.youtube.com/embed/t1MOHCfsdvk"
+                  src="https://www.youtube-nocookie.com/embed/t1MOHCfsdvk"
                   title="Spec-driven Development Demo"
                   frameBorder="0"
                   allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"