feat(frontend): adopt zibll site-layout-1/2/3 float dual-column system

Wire settings-driven sidebar visibility and body site-layout classes,
replace content-layout CSS grid with Zibll float geometry, move sidebar
DOM to content-wrap sibling across single/archive/page/home, and add
post meta show_layout overrides.

inc/classes/class-aksrt-post-meta-box.php

@@ -176,6 +176,21 @@ class AKSRT_Post_Meta_Box {
             <option value="mini" <?php selected($meta['layout_override'], 'mini'); ?>><?php esc_html_e('迷你', 'aksrt'); ?></option>
         </select>
 
+        <p><strong><?php esc_html_e('侧栏布局（Zibll show_layout）', 'aksrt'); ?></strong></p>
+        <?php
+        $show_layout = (string) get_post_meta($post->ID, '_aksrt_show_layout', true);
+        if (!in_array($show_layout, ['no_sidebar', 'sidebar_left', 'sidebar_right'], true)) {
+            $show_layout = '';
+        }
+        ?>
+        <select name="aksrt_show_layout" class="widefat">
+            <option value="" <?php selected($show_layout, ''); ?>><?php esc_html_e('跟随全局', 'aksrt'); ?></option>
+            <option value="no_sidebar" <?php selected($show_layout, 'no_sidebar'); ?>><?php esc_html_e('无侧栏', 'aksrt'); ?></option>
+            <option value="sidebar_right" <?php selected($show_layout, 'sidebar_right'); ?>><?php esc_html_e('右侧栏', 'aksrt'); ?></option>
+            <option value="sidebar_left" <?php selected($show_layout, 'sidebar_left'); ?>><?php esc_html_e('左侧栏', 'aksrt'); ?></option>
+        </select>
+        <p class="description"><?php esc_html_e('覆盖全局侧栏开关与左右位置，仅影响本文/本页。', 'aksrt'); ?></p>
+
         <p><strong><?php esc_html_e('头图模式', 'aksrt'); ?></strong></p>
         <select name="aksrt_post_meta[header_image_mode]" class="widefat">
             <option value="" <?php selected($meta['header_image_mode'], ''); ?>><?php esc_html_e('跟随全局', 'aksrt'); ?></option>
@@ -349,6 +364,17 @@ class AKSRT_Post_Meta_Box {
         if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return;
         if (!current_user_can('edit_post', $post_id)) return;
 
+        // Zibll show_layout (independent of list layout_override).
+        $show_layout = isset($_POST['aksrt_show_layout']) ? sanitize_key((string) wp_unslash($_POST['aksrt_show_layout'])) : '';
+        if (!in_array($show_layout, ['no_sidebar', 'sidebar_left', 'sidebar_right'], true)) {
+            $show_layout = '';
+        }
+        if ($show_layout !== '') {
+            update_post_meta($post_id, '_aksrt_show_layout', $show_layout);
+        } else {
+            delete_post_meta($post_id, '_aksrt_show_layout');
+        }
+
         // §3.8 Quick / Bulk edit — separate code path (merge mode)
         if (!empty($_POST['aksrt_qe_flag'])) {
             $this->save_quick_edit($post_id);