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.

_javascript/modules/layouts/sidebar.js

@@ -1,7 +1,19 @@
-import { modeWatcher } from '../components/mode-watcher';
-import { sidebarExpand } from '../components/sidebar';
+const ATTR_DISPLAY = 'sidebar-display';
+const $sidebar = document.getElementById('sidebar');
+const $trigger = document.getElementById('sidebar-trigger');
+const $mask = document.getElementById('mask');
+
+class SidebarUtil {
+  static #isExpanded = false;
+
+  static toggle() {
+    this.#isExpanded = !this.#isExpanded;
+    document.body.toggleAttribute(ATTR_DISPLAY, this.#isExpanded);
+    $sidebar.classList.toggle('z-2', this.#isExpanded);
+    $mask.classList.toggle('d-none', !this.#isExpanded);
+  }
+}
 
 export function initSidebar() {
-  modeWatcher();
-  sidebarExpand();
+  $trigger.onclick = $mask.onclick = () => SidebarUtil.toggle();
 }