fix: rerender mermaid diagrams on theme change (#509)

Make mermaid render diagrams on manual toggle between themes, after initial page load

layouts/partials/scripts.html

@@ -37,9 +37,32 @@
   {{- $mermaidJS := resources.Get "lib/mermaid/mermaid.min.js" | fingerprint -}}
   <script defer src="{{ $mermaidJS.RelPermalink }}" integrity="{{ $mermaidJS.Data.Integrity }}"></script>
   <script>
-    document.addEventListener("DOMContentLoaded", function () {
+    document.addEventListener("DOMContentLoaded", () => {
+      // Store original mermaid code for each diagram
+      document.querySelectorAll(".mermaid").forEach(el => {
+        el.dataset.original = el.innerHTML;
+      });
+
       const theme = document.documentElement.classList.contains("dark") ? "dark" : "default";
       mermaid.initialize({ startOnLoad: true, theme: theme });
+
+      let timeout;
+      new MutationObserver(() => {
+        clearTimeout(timeout);
+        timeout = setTimeout(() => {
+          const theme = document.documentElement.classList.contains("dark") ? "dark" : "default";
+          document.querySelectorAll(".mermaid").forEach(el => {
+            // Reset to original content, preserving HTML
+            el.innerHTML = el.dataset.original;
+            el.removeAttribute("data-processed");
+          });
+          mermaid.initialize({ startOnLoad: true, theme: theme });
+          mermaid.init();
+        }, 150);
+      }).observe(document.documentElement, {
+        attributes: true,
+        attributeFilter: ["class"]
+      });
     });
   </script>
 {{- end -}}