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/DiviLibraryStore.php

@@ -4,6 +4,11 @@ declare(strict_types=1);
 
 namespace LIT\MCP\Integrations\Divi\Library;
 
+use LIT\MCP\Abilities\WriteFailed;
+use LIT\MCP\Integrations\WordPress\Content\NewDraft;
+use RuntimeException;
+use Throwable;
+use WP_Error;
 use WP_Post;
 use WP_Term;
 
@@ -126,6 +131,50 @@ class DiviLibraryStore
         ];
     }
 
+    /** Client text when the terms or meta of a new entry could not be written. */
+    public const REASON_CREATE = 'Der Bibliothekseintrag konnte nicht vollständig angelegt werden.';
+
+    /**
+     * A published entry with the terms and meta of $spec and empty content (E4; the layout follows
+     * through DiviSaver::saveNew()). All or nothing through $draft (ruling P6, the transaction of
+     * lit/content-create): a refused insert or missing taxonomies create nothing; a failed term or
+     * meta write deletes the entry again (write_failed), or reports partial_write and logs it
+     * when that delete fails; a throwing insert hook is a partial write without ID.
+     *
+     * @throws WriteFailed
+     */
+    public function create(LibraryItemSpec $spec, NewDraft $draft): int
+    {
+        $missing = $this->missingTaxonomies();
+        if ($missing !== []) {
+            throw WriteFailed::rolledBack(
+                'Die Divi-Bibliothek ist in dieser Anfrage nicht geladen.',
+                detail: 'Divi Library taxonomies not registered: ' . implode(', ', $missing)
+            );
+        }
+
+        $id = $draft->insert([
+            'post_type' => self::POST_TYPE,
+            'post_status' => 'publish',
+            'post_title' => $spec->title,
+            'post_content' => '',
+        ]);
+        if ($id instanceof WP_Error) {
+            throw WriteFailed::rolledBack(
+                'WordPress hat den Bibliothekseintrag abgelehnt.',
+                detail: 'wp_insert_post refused the library entry: ' . $id->get_error_message()
+            );
+        }
+
+        try {
+            $this->describeNew($id, $spec);
+        } catch (Throwable $e) {
+            $draft->discard($id, $e, self::REASON_CREATE);
+        }
+
+        return $id;
+    }
+
     /**
      * Library taxonomies not registered in this request (F2: Divi registers them in
      * ET_Builder_Library; fixture finding 6: not in every context).
@@ -140,6 +189,27 @@ class DiviLibraryStore
         ));
     }
 
+    /**
+     * Terms and meta of $spec on the new entry $id, each checked.
+     *
+     * @throws RuntimeException
+     */
+    private function describeNew(int $id, LibraryItemSpec $spec): void
+    {
+        foreach ($spec->terms() as $taxonomy => $terms) {
+            $result = wp_set_object_terms($id, $terms, $taxonomy);
+            if ($result instanceof WP_Error) {
+                throw new RuntimeException(sprintf('terms %s: %s', $taxonomy, $result->get_error_message()));
+            }
+        }
+        foreach ($spec->meta() as $key => $value) {
+            update_post_meta($id, $key, $value);
+            if ((string) get_post_meta($id, $key, true) !== $value) {
+                throw new RuntimeException(sprintf('meta %s of library entry %d not stored', $key, $id));
+            }
+        }
+    }
+
     /** @return list<WP_Term> */
     private function terms(int $id, string $taxonomy): array
     {