feat: Divi tools edit Theme Builder layouts; visible layouts need confirm

TB layouts load through ThemeBuilderAccess (P12), live layouts (attached +
enabled, Q8) need a dry run and confirm (Q9) and get the shared restore point
of VisibleEdits, extracted from GlobalEdits (Q2: backup when revisions are
off, P9 refusals, P14 naming). divi/post-content only in body layouts (F22),
also for nested stored nodes. SaveScope::ThemeBuilderLayout sets Divi flags
and clears site CSS + TB cache.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/Integrations/Divi/Compose/TreeEditor.php

@@ -81,7 +81,8 @@ final class TreeEditor
     public function insert(array $position, array $blocks): ?string
     {
         foreach ($blocks as $block) {
-            $violation = $this->rules->violation($position['parent'], GlobalInstance::effectiveName($block));
+            $violation = $this->rules->violation($position['parent'], GlobalInstance::effectiveName($block))
+                ?? $this->rules->nestedAreaViolation($block);
             if ($violation !== null) {
                 return $violation;
             }