fix(docs): prevent mermaid diagram overflow on mobile

Add scrollable container rules for .mermaid-diagram in mobile
media query. SVG diagrams now scroll horizontally within their
container instead of extending the page width and obscuring
the hamburger menu.

docs/static/style.css

@@ -621,4 +621,16 @@ th {
   td code {
     white-space: normal;
   }
+
+  /* Make mermaid diagrams scrollable on mobile */
+  .mermaid-diagram {
+    overflow-x: auto;
+    max-width: calc(100vw - 2rem);
+  }
+
+  .mermaid-diagram svg {
+    display: block;
+    max-width: none;
+    /* Allow SVG to be wider than container */
+  }
 }