feat(runtime): 全站前端脚本统一接入 AksrtFrontend 全局 DOM 生命周期

- rehydrate.js 新增 boot()/aksrt:ready 事件，支持 boot 后晚注册立即以 init 触发
- aksrt-runtime.js 初始加载改走 AksrtFrontend.boot，tooltip/倒计时注册为组件
- 约 30 个前端脚本（首页、评论、支付、路由、页面叶子、widgets）
  从直接 DOMContentLoaded 迁移为 AksrtFrontend.register，并加幂等标记
- section-navs 依赖改为 aksrt-runtime，保证注册时序
- 清理死代码：删除孤儿 loader.js/main.js 及 runtime/page-navs 遗留副本
- loader.js 移除已迁移模块的 tbquire 路径映射，main.js 相应瘦身
- build-public-assets.mjs 增加 runtime/main.min.js 自动压缩步骤
- 新增 4 个契约测试（homepage-dom/rehydrate-runtime/global-dom-init/
  public-bundle-parity），3 个既有 harness 适配注册表初始化方式

assets/js/enhancements.js

@@ -21,6 +21,8 @@
   var isAutoplay = false;
   var lastTrigger = null;
   var previousBodyOverflow = '';
+  var globalsBound = false;
+  var scrollDirectionBound = false;
   var EXCLUDE_SEL = '.no-imgbox,.no-lightbox,.avatar,.img-icon,.avatar-badge,.aksrt-avatar,[data-no-lightbox],[data-aksrt-lightbox="0"]';
   var TRIGGER_SEL = '[data-aksrt-lightbox="1"] img,.aksrt-lightbox-trigger img,.imgbox-container img,.comment-content .box-img';
   var ANCHOR_TRIGGER_SEL = 'a[data-aksrt-lightbox-trigger]';
@@ -496,7 +498,9 @@
     return openLightbox(item.fullSrc, item.caption, gallery.items, gallery.index, img);
   }
 
-  function initLightbox() {
+  function initLightbox(root, reason) {
+    if (globalsBound) return;
+    globalsBound = true;
     document.addEventListener('click', function (event) {
       if (!lightboxEnabled() || !(event.target instanceof Element)) return;
 
@@ -527,7 +531,9 @@
 
   // Scroll direction is handled by aksrt-runtime.js. Keep the prefixed
   // classes in sync for the remaining CSS consumers.
-  function initScrollDirection() {
+  function initScrollDirection(root, reason) {
+    if (scrollDirectionBound || !document.body) return;
+    scrollDirectionBound = true;
     var body = document.body;
 
     function sync() {
@@ -547,8 +553,8 @@
     }, { passive: true });
   }
 
-  document.addEventListener('DOMContentLoaded', function () {
-    initLightbox();
-    initScrollDirection();
+  window.AksrtFrontend.register('aksrt-enhancements', function (root, reason) {
+    initLightbox(root, reason);
+    initScrollDirection(root, reason);
   });
 })();