fix: mermaid rendering with startOnLoad:false + explicit run()

Module scripts are deferred; startOnLoad:true misses DOMContentLoaded.
Use startOnLoad:false and await mermaid.run() after DOM transformation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: emmanuelknafo

_includes/head-custom.html

@@ -1,12 +1,13 @@
 <script type="module">
   import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs';
-  mermaid.initialize({ startOnLoad: true });
+  mermaid.initialize({ startOnLoad: false });
   document.querySelectorAll('pre > code.language-mermaid').forEach(el => {
     const div = document.createElement('div');
     div.className = 'mermaid';
     div.textContent = el.textContent;
     el.parentElement.replaceWith(div);
   });
+  await mermaid.run();
 </script>
 <style>
   .mermaid { text-align: center; }