Fix repertoire column scrolling + admin TOC duplication

- repertoire.css: add min-height: 0 to column <ul> scroll containers so
  grid 1fr row shrinks below content and overflow-y: auto activates
- admin-toc.js: add __adminTocBuilt guard + nav.children check to prevent
  double population when loaded both via admin.min.js and direct <script>
- admin-toc.php: remove duplicate <script src="admin-toc.js"> tag —
  JS is already bundled in admin.min.js

app/public/assets/js/app/admin-toc.js

@@ -4,14 +4,22 @@
  *
  * Renders nav links from section[aria-labelledby] headings inside #main-content.
  * Hides the TOC aside if fewer than 2 sections exist.
+ *
+ * Guarded: only runs once even if loaded multiple times (e.g. via bundle + direct <script>).
  */
 (function () {
+    if (window.__adminTocBuilt) return;
+    window.__adminTocBuilt = true;
+
     function build() {
         var main = document.getElementById('main-content');
         var nav = document.getElementById('admin-toc-list');
         var aside = document.getElementById('admin-toc');
         if (!main || !nav || !aside) return;
 
+        // Guard against double population (nav already has children from a prior run)
+        if (nav.children.length > 0) return;
+
         var sections = main.querySelectorAll('section[aria-labelledby]');
         if (sections.length < 2) {
             aside.hidden = true;