feat(website): add GitHub nav link and git clone to quick start

- Add GitHub link to nav bar on both index and docs pages
- Add git clone + cd commands to Quick Start terminal block

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

docs/website/docs.html

@@ -63,6 +63,7 @@
         <a href="index.html" class="nav-link">Home</a>
         <a href="index.html#features" class="nav-link">Features</a>
         <a href="docs.html" class="nav-link nav-link--active">Docs</a>
+        <a href="https://github.com/staack/the-other-dude" class="nav-link" rel="noopener">GitHub</a>
       </div>
     </div>
   </nav>