fix(single): close remaining live gaps vs Zibll demo

Align runtime --sidebar-width (300→311), --main-radius, and
body.nav-fixed 88px reserve; enqueue single-post CSS parts directly;
match Zibll action buttons and author avatar DOM; tighten dual-column
tokens after comparing blog.rutua.cn with demo.zibll.com.

inc/classes/scripts-traits/trait-aksrt-scripts-part-1b.php

@@ -192,6 +192,32 @@ trait AKSRT_Scripts_Part_1b {
 
         // 单篇文章：所有 single 相关样式
         if ($is_single_post) {
+            // Prefer discrete enqueues over CSS @import (cache-bust + parallel load).
+            $single_parts = [
+                'zibll-utilities',
+                'single-post/shell',
+                'single-post/content',
+                'single-post/code-blocks',
+                'single-post/navigation',
+                'single-post/cover',
+                'single-post/author-actions',
+                'single-post/related-toc',
+                'single-post/hidden-content',
+            ];
+            $single_dep = $deps[0] ?? $core_dep;
+            foreach ($single_parts as $part) {
+                $path = get_template_directory() . '/assets/css/frontend/' . $part . '.css';
+                if (!file_exists($path)) {
+                    continue;
+                }
+                wp_enqueue_style(
+                    'aksrt-' . str_replace('/', '-', $part),
+                    $base_uri . '/assets/css/frontend/' . $part . '.css',
+                    is_string($single_dep) ? [$single_dep] : (array) $deps,
+                    filemtime($path) ?: $version
+                );
+            }
+            // Keep aggregator handle for any third-party deps that target it.
             $enqueue_module('single-post');
             $enqueue_module('post-card');     // 相关推荐使用 post-card 局部样式
             $enqueue_module('comments');