feat(nav): rewrite top header to zibll 1:1 DOM/CSS/JS contract

Replace hybrid site-nav/drawer shell with zibll navbar-top layouts 1/2/3,
body.mobile-navbar-show drawer, wired NavWalker + aksrt_menu_options meta,
nav_folding/chevron, VIP switches, and SPA/PHP schema parity. No dual-class
compat paths.

assets/js/share-data-builder.js

@@ -30,7 +30,7 @@
   function siteName() {
     return (
       metaContent(['meta[property="og:site_name"]']) ||
-      (document.querySelector('.site-title, .logo-text, .site-nav__logo') || {}).textContent ||
+      (document.querySelector('.site-title, .logo-text, .navbar-logo') || {}).textContent ||
       document.title ||
       ''
     ).trim();