Fix sidebar scroll: use offsetTop relative to sidebar instead of scrollIntoView

Co-authored-by: sarzhann <32760183+sarzhann@users.noreply.github.com>
Agent-Logs-Url: https://github.com/vespa-engine/documentation/sessions/7dcf5901-91bf-45f0-8d73-27a8ab69629d

Author: Copilot

_includes/sidebar.html

@@ -167,8 +167,14 @@
         });
     });
 
-    const current = document.querySelector('#sidebar .sidebar-current');
-    if (current) current.scrollIntoView({ block: 'nearest' });
+    const sidebar = document.getElementById('sidebar');
+    const current = sidebar && sidebar.querySelector('.sidebar-current');
+    if (sidebar && current) {
+        const sidebarRect = sidebar.getBoundingClientRect();
+        const currentRect = current.getBoundingClientRect();
+        const offset = currentRect.top - sidebarRect.top + sidebar.scrollTop;
+        sidebar.scrollTop = offset - sidebar.clientHeight / 2 + currentRect.height / 2;
+    }
 
     function setNavbarHeight() {
         const nav = document.querySelector('nav.sticky-top');