fix(single): align article code blocks with the reference theme

The article body ran two highlighting pipelines at once: the runtime
EnlighterJS pass (same one the comment area uses) plus a bespoke
precode.js enhancer, and a hand-rolled .code-block skin. The two
disagreed, so rendered blocks carried a dark #282c34 card with 15px
padding, 14px text, a border and a second copy button stacked on top of
the EnlighterJS toolbar.

Drop the parallel path and let one pipeline own code blocks:
- delete precode.js, single-post/code-blocks.css and the unused
  assets/js/enlighter copy that only precode.js referenced
- drop the now-dead has_code requirement (PHP scan + feature enqueue)
- render pre exactly as the reference does: bootstrap's pre box
  (9.5px padding / 13px / radius 4) plus main.css's muted background,
  with the EnlighterJS theme supplying the skin

Also scope the inline-code skin to :not(pre code) so it stops painting
the block background pink, and remap the toolbar copy glyph: \f0ea is
the clipboard in FA4 but "paste" in FA5; the clipboard is \f328.

Verified against the reference at 1440px both themes: pre 13px/18.57,
9.5px padding, radius 4, muted background; EnlighterJS block heights
151.31 / 60.38 match exactly.

src/Core/ScriptsPart1b.php

@@ -49,8 +49,9 @@ trait ScriptsPart1b {
             wp_add_inline_style('jio-public', '.lazyloaded{--lazy-animation:lazy_scale!important;}');
         }
 
-        // 代码高亮的「最大高度」与「扩展按钮」由后台设置驱动。runtime 的
-        // enlighter 路径（评论区 [code] 等）不走 precode.js，需要这两条规则兜底。
+        // 代码高亮的「最大高度」与「扩展按钮」由后台设置驱动。
+        // 高亮统一走 runtime 的 enlighter 路径，这两条规则对文章正文、
+        // 评论区 [code] 与未高亮的裸 pre 一并生效。
         if (class_exists('\Jio\Settings\Settings')) {
             $code_highlight_css = \Jio\Settings\Settings::get_code_highlight_config();
             if (!empty($code_highlight_css['enabled'])) {
@@ -239,7 +240,6 @@ trait ScriptsPart1b {
 			);
 
 			$single_features = [
-				'has_code'           => 'single-post/code-blocks',
 				'needs_navigation'   => 'single-post/navigation',
 				'needs_cover'        => 'single-post/cover',
 				'needs_related_toc'  => 'single-post/related-toc',