Make model column sticky when scrolling tables horizontally

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

style.css

@@ -384,7 +384,14 @@ tbody tr.row-group-break td {
     border-top: 2px solid var(--border);
 }
 
-/* ── Legend ───────────────────────────────────────────── */
+/* ── Sticky first column in scrollable tables ─────────── */
+.table-scroll th:first-child,
+.table-scroll td:first-child {
+    position: sticky;
+    left: 0;
+    z-index: 1;
+    background: var(--bg);
+}
 .legend-section {
     margin: 2rem 0;
     padding-top: 1.5rem;