feat(site-builder): Layers shows array-prop items, unplaced nodes, and scrolls

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

craft/src/styles/editor.css

@@ -1919,3 +1919,13 @@ body {
   cursor: pointer;
   padding: 0 4px;
 }
+
+/* --------------------------------------------------------------------------
+   Layers: display-only rows derived from a composite's array props
+   (Features Grid features, Tabs tabs, ...). Dimmer than real node rows and
+   with no disclosure column, so they don't read as draggable Craft nodes.
+   -------------------------------------------------------------------------- */
+.layer-virtual-row:hover {
+  background: var(--color-bg-hover);
+  color: var(--color-text);
+}