fix(posts): repair the load-more skeleton and align it with the reference

Clicking 加载更多 showed no skeleton at all, and the placeholder shape did
not match the reference theme's post cards.

- Class-name mismatch: pagination.js queried .post-ajax-loader while every
  PHP producer emits .post_ajax_loader, so showSkeleton() never found a
  target and the loader stayed hidden. Accept both spellings.
- Inline display:none on the loader (pagination, comments, widget tab
  panes) outranked .is-loading, so even the correct selector could not
  reveal it. Drop the inline style; the reference uses a bare
  <div class="post_ajax_loader"> and toggles visibility from JS.
- loadNextPage() set indicator.style.display = "flex", which forced the
  .posts-item.card skeleton blocks (inline-block layout) into a single
  row instead of stacking vertically — the visible symptom. Remove those
  inline writes and drive .is-loading from CSS for every surface.
- Scope the hide/show rules on the class itself rather than requiring an
  .ajaxpager ancestor: homepage tab panes, archive streams and comment
  lists sit at three different depths.
- Rebuild aksrt_render_placeholder() on zib_get_post_placeholder's
  structure — list = t1/k1/k2 + two s1, card = t1 item-heading/k2 + two
  s1, thumb wrapped in post-graphic + radius8 item-thumbnail, all carrying
  ajax-item so the loader is not mistaken for a real card.
- Add mini/mini_thumb modes so ContentRenderer::placeholder() stops
  hand-rolling the same markup; normalize its 'lists' arg to 'list'.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/js/core/pagination.js

@@ -31,7 +31,6 @@
       var failed = false;
       var clickTarget = container.querySelector(".next-page.ajax-next, .ias-btn") || container;
       var loadMoreBtn = container.querySelector("[data-aksrt-load-more]") || clickTarget;
-      var indicator = container.querySelector(".post_ajax_loader");
       var successfulAutoLoads = 0;
       var iasMax = isComment
         ? ((window.aksrtData && typeof aksrtData.commentIasMax !== "undefined") ? parseInt(aksrtData.commentIasMax, 10) : 0)
@@ -54,7 +53,8 @@
 
       function showSkeleton() {
         if (!target) return;
-        var loader = target.querySelector(".post-ajax-loader");
+        // PHP 产出下划线类名 post_ajax_loader；这里同时兼容连字符写法。
+        var loader = target.querySelector(".post_ajax_loader, .post-ajax-loader");
         if (loader) {
           loader.classList.add("is-loading");
         }
@@ -62,7 +62,7 @@
 
       function hideSkeleton() {
         if (!target) return;
-        var loader = target.querySelector(".post-ajax-loader");
+        var loader = target.querySelector(".post_ajax_loader, .post-ajax-loader");
         if (loader) {
           loader.classList.remove("is-loading");
         }
@@ -107,7 +107,8 @@
         }
 
         loading = true;
-        if (indicator) indicator.style.display = "flex";
+        // 骨架开关统一走 .is-loading（modal-runtime.css），不要直接写
+        // display:flex —— 那会让卡片型骨架挤成一行而不是纵向堆叠。
         if (loadMoreBtn) {
           loadMoreBtn.classList.add("is-loading");
           loadMoreBtn.textContent = loadingText;
@@ -197,7 +198,6 @@
           .finally(function () {
             loading = false;
             hideSkeleton();
-            if (indicator) indicator.style.display = "none";
             if (loadMoreBtn && !loadMoreBtn.classList.contains("ajax-nomore") && !failed) {
               loadMoreBtn.classList.remove("is-loading");
               loadMoreBtn.innerHTML = triggerText;