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/captcha-front.js

@@ -121,8 +121,11 @@
     TOKEN_FIELDS: TOKEN_FIELDS
   });
 
-  function scan() {
-    var mounts = document.querySelectorAll('[data-aksrt-captcha-config]');
+  function scan(root, reason) {
+    var scope = root && root.querySelectorAll ? root : document;
+    var mounts = [];
+    if (scope.nodeType === 1 && scope.matches('[data-aksrt-captcha-config]')) mounts.push(scope);
+    Array.prototype.push.apply(mounts, scope.querySelectorAll('[data-aksrt-captcha-config]'));
     Array.prototype.forEach.call(mounts, function (mount) {
       if (mount.dataset.aksrtCaptchaBound) return;
       var config;
@@ -545,13 +548,5 @@
     }
   }
 
-  if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', scan);
-  else setTimeout(scan, 0);
-
-  if (window.MutationObserver) {
-    new MutationObserver(function (mutations) {
-      var shouldScan = mutations.some(function (mutation) { return mutation.addedNodes && mutation.addedNodes.length; });
-      if (shouldScan) scan();
-    }).observe(document.documentElement, { childList: true, subtree: true });
-  }
+  window.AksrtFrontend.register('aksrt-captcha-front', scan);
 })();