added scrollspy for TOC highlighting, theme toggle support, and dark/light mode handling

site/src/jsMain/resources/index.html

@@ -21,6 +21,18 @@
     <meta charset="utf-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1" />
     <title>Compose HTML SPA</title>
+    <!-- GitHub Markdown CSS (light and dark). We toggle these from the app. -->
+    <link
+      id="md-light"
+      rel="stylesheet"
+      href="https://cdn.jsdelivr.net/npm/github-markdown-css@5.4.0/github-markdown.css"
+    />
+    <link
+      id="md-dark"
+      rel="stylesheet"
+      href="https://cdn.jsdelivr.net/npm/github-markdown-css@5.4.0/github-markdown-dark.css"
+      disabled
+    />
     <!-- Bootstrap 5.3 CSS -->
     <link
       href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/css/bootstrap.min.css"
@@ -33,6 +45,17 @@
       rel="stylesheet"
       href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.3/font/bootstrap-icons.min.css"
     />
+    <style>
+      /* Visual polish for markdown area */
+      .markdown-body {
+        box-sizing: border-box;
+        min-width: 200px;
+        line-height: 1.6;
+      }
+      .markdown-body > :first-child { margin-top: 0 !important; }
+      .markdown-body table { margin: 1rem 0; }
+      .markdown-body pre { padding: .75rem; border-radius: .375rem; }
+    </style>
   </head>
   <body>
     <div id="root"></div>