feat: lit/library-save creates library entries like Divi (E4)

Reuses NewDraft for insert and rollback (P6), requires edit_global_library
for scope global (P7), refuses opaque and global roots before wrapping (P11)
and checks the node with StoredNodeGuard. The source page is never written.

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

src/Integrations/Divi/Library/LibraryAccess.php

@@ -120,6 +120,34 @@ class LibraryAccess
         return $this->isGlobal($item) ? $this->roles->refusal('edit_global_library') : null;
     }
 
+    /**
+     * Creating an entry: canList(), publish_posts of et_pb_layout (library entries are always
+     * published, F2), the role option save_library and the Tools-tab gate; a global entry
+     * additionally edit_global_library (ruling P7 – the same option as for editing one, F12).
+     */
+    public function canSave(bool $global = false): ?WP_Error
+    {
+        $refusal = $this->canList();
+        if ($refusal !== null) {
+            return $refusal;
+        }
+
+        $type = get_post_type_object(DiviLibraryStore::POST_TYPE);
+        $publish = is_object($type) && isset($type->cap->publish_posts)
+            ? (string) $type->cap->publish_posts
+            : 'publish_posts';
+        if (! current_user_can($publish)) {
+            return Errors::forbidden('Keine Berechtigung, Einträge der Divi-Bibliothek anzulegen (publish_posts).');
+        }
+
+        $refusal = $this->roles->refusal('save_library') ?? $this->writableGate();
+        if ($refusal !== null || ! $global) {
+            return $refusal;
+        }
+
+        return $this->roles->refusal('edit_global_library');
+    }
+
     /** Refusal while the Tools tab keeps this connection from writing to the library. */
     public function writableGate(): ?WP_Error
     {