perf: speed up page rendering and jekyll build process (#2034)

- Ensure inline scripts execute after the DOM has fully loaded.
- Use Rollup to bundle the theme-mode and Mermaid scripts, reducing the number of Jekyll include snippets.

_layouts/post.html

@@ -6,7 +6,8 @@ panel_includes:
 tail_includes:
   - related-posts
   - post-nav
-  - comments
+script_includes:
+  - comment
 ---
 
 {% include lang.html %}