[CMS-VISUAL] F2: 门户布局区块输出稳定 id + data-plb-id 锚点（display:contents 零布局影响）+ postMessage 预览监听脚本（门户侧 50 测试绿）

src/main/resources/templates/themes/default/home.html

@@ -26,8 +26,12 @@
     <!-- 首页布局模式（docs/16 §4.4）：home_layout 落库后按区块序列渲染（common 兜底骨架，本主题不另设形态） -->
     <th:block th:if="${layoutBlocks != null}">
         <th:block th:replace="~{'themes/common/fragments/home-blocks' :: style}" />
+        <th:block th:replace="~{'themes/common/fragments/home-blocks' :: previewScript}" />
+        <!-- F2：data-plb-id 锚点（display:contents）供编辑器实时预览 postMessage 重排 -->
         <th:block th:each="block : ${layoutBlocks}">
-            <th:block th:replace="~{'themes/common/fragments/home-blocks' :: render(${block})}" />
+            <div class="plb-anchor" th:attr="data-plb-id=${block['id']}" style="display:contents">
+                <th:block th:replace="~{'themes/common/fragments/home-blocks' :: render(${block})}" />
+            </div>
         </th:block>
     </th:block>