feat: lit/content-create with Divi short form

New input divi (1-30 sections, short form like lit-divi-insert) builds a Divi 5
layout in one divi/placeholder. The whole description is checked before the
insert (Divi's map for "no entry yet"); the draft is inserted with its normal
WordPress fields only, then DiviContentComposer composes again bound to the new
entry and stores it via DiviSaver::saveNew (same kses window as save(), strict
DiviFlags). A refusal or failure deletes the draft. Result adds tree_rev and the
outline.

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

src/Integrations/Divi/Pages/DiviContentComposer.php

@@ -0,0 +1,119 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Integrations\Divi\Pages;
+
+use LIT\MCP\Abilities\Errors;
+use LIT\MCP\Integrations\Divi\BlockTree\Block;
+use LIT\MCP\Integrations\Divi\BlockTree\Document;
+use LIT\MCP\Integrations\Divi\BlockTree\NodeIndex;
+use LIT\MCP\Integrations\Divi\BlockTree\Outline;
+use LIT\MCP\Integrations\Divi\BlockTree\Serializer;
+use LIT\MCP\Integrations\Divi\Design\DesignSystemReader;
+use LIT\MCP\Integrations\Divi\Schema\DiviModules;
+use LIT\MCP\Integrations\WordPress\Content\ContentComposer;
+use LIT\MCP\Integrations\WordPress\Schema\ContentSchema;
+use WP_Error;
+
+/**
+ * Divi short form for lit/content-create (spec §6.2): the sections become a Divi 5 layout in
+ * exactly one divi/placeholder – inserted by TreeEditor like the first section of an empty page
+ * (ruling S9) – stored through DiviSaver's kses window, with the builder flags (DiviFlags, S11).
+ *
+ * Allow map (ruling S22) for an entry that does not exist yet: check() runs before the insert
+ * with the composition bound to post ID 0 – Divi's own registry for "no entry" (get_options(0)
+ * treats it like a post; live the same options as for a page, only the taxonomy choices of
+ * post_categories/post_tags differ). write() composes again, bound to the new entry – the
+ * layout that is stored always passed that entry's live map, like every other Divi write
+ * (DiviWriter::composition). Should the entry's map refuse something (an option Divi offers
+ * only for other types), write() returns the errors and lit/content-create deletes the draft.
+ *
+ * Every client string goes through Composer (AttrWriter / ShortformWriter) – the single choke
+ * point that makes the kses bypass safe (spec D7).
+ */
+final class DiviContentComposer implements ContentComposer
+{
+    public function __construct(
+        private ContentSchema $schema,
+        private DiviComposition $composition,
+        private DiviSaver $saver,
+        private DesignSystemReader $design
+    ) {
+    }
+
+    public function available(): bool
+    {
+        return DiviModules::isAvailable();
+    }
+
+    public function check(string $postType, array $sections): ?WP_Error
+    {
+        if (! $this->schema->diviEnabled($postType)) {
+            return Errors::invalidInput(
+                'Für diesen Inhaltstyp ist der Divi-Builder nicht aktiviert; nichts wurde angelegt.',
+                ['divi' => sprintf('Divi-Builder für "%s" nicht aktiv', $postType)]
+            );
+        }
+
+        $layout = $this->layout($this->composition->forPost(0), $sections);
+
+        return $layout instanceof WP_Error ? $layout : null;
+    }
+
+    public function write(int $postId, string $postType, array $sections): array|WP_Error
+    {
+        $composition = $this->composition->forPost($postId);
+        $layout = $this->layout($composition, $sections);
+        if ($layout instanceof WP_Error) {
+            return $layout;
+        }
+
+        $index = NodeIndex::build($layout['document']);
+        $warnings = $composition->warnings()->collect($index, $layout['blocks']);
+        $outline = new Outline($this->design->read()->presetNames());
+        $text = $outline->text($outline->rows($index));
+        if ($outline->wasTruncated()) {
+            $warnings[] = DiviWriter::OUTLINE_TRUNCATED;
+        }
+
+        $saved = $this->saver->saveNew($postId, Serializer::document($layout['document']));
+
+        return ['warnings' => array_merge($warnings, $saved), 'outline' => $text];
+    }
+
+    /**
+     * The whole description composed and inserted into an empty document – or every error.
+     *
+     * @param list<mixed> $sections
+     * @return array{document: Document, blocks: list<Block>}|WP_Error
+     */
+    private function layout(DiviComposition $composition, array $sections): array|WP_Error
+    {
+        if ($sections === []) {
+            return Errors::invalidInput('Kein Divi-Inhalt angegeben; nichts wurde angelegt.', [
+                'divi' => 'mindestens ein Abschnitt',
+            ]);
+        }
+
+        $composed = $composition->composer()->compose(array_values($sections), null, 'divi');
+        if ($composed['errors'] !== []) {
+            return $composed['invalid_paths'] !== []
+                ? Errors::invalidAttrPath($composed['errors'])
+                : Errors::invalidInput('Divi-Inhalt ist ungültig; nichts wurde angelegt.', $composed['errors']);
+        }
+
+        $document = new Document();
+        $violation = $composition->editor()->insert(
+            ['container' => $document, 'parent' => null, 'index' => PHP_INT_MAX],
+            $composed['blocks']
+        );
+        if ($violation !== null) {
+            return Errors::invalidInput('Divi-Inhalt passt nicht auf die Seite; nichts wurde angelegt.', [
+                'divi' => $violation,
+            ]);
+        }
+
+        return ['document' => $document, 'blocks' => $composed['blocks']];
+    }
+}

src/Integrations/Divi/Pages/DiviSaver.php

@@ -36,7 +36,8 @@ use WP_Post;
  * transition_post_status, wp_after_insert_post and third-party listeners. No MCP input reaches
  * those hooks except the content itself (already cleaned); anything a third-party hook writes
  * there is saved without kses, as it would be for an administrator. The rollback write in
- * restore() uses the same window with the previous stored content.
+ * restore() uses the same window with the previous stored content; saveNew() (the first layout
+ * of a new draft, lit/content-create) uses it for its single wp_update_post().
  *
  * Divi's own save filters are NOT kses and are never removed (ruling S7, defense in depth):
  * Security::initialize() (Divi 5.2.1 Security.php:74-81) registers on wp_insert_post_data
@@ -116,6 +117,34 @@ class DiviSaver
         return ['revision_id' => $revisionId, 'warnings' => $warnings];
     }
 
+    /**
+     * The first content of a brand-new draft (lit/content-create with divi, which inserted the
+     * draft with its normal WordPress fields – title and excerpt went through kses as usual).
+     * Same kses window as save(), holding only this wp_update_post() and its hooks; no restore
+     * point (the draft has no earlier state) and no static CSS to clear. The Divi flags are part
+     * of the write here: without them the new entry is no Divi layout. Every failure throws –
+     * the caller deletes the draft (all or nothing).
+     *
+     * @return list<string> Warnings (CHANGED_ON_SAVE).
+     * @throws RuntimeException
+     */
+    public function saveNew(int $postId, string $content): array
+    {
+        $result = $this->withoutKses(
+            static fn (): int|WP_Error => wp_update_post(wp_slash(['ID' => $postId, 'post_content' => $content]), true)
+        );
+        if ($result instanceof WP_Error || $result === 0) {
+            $message = $result instanceof WP_Error ? $result->get_error_message() : 'returned 0';
+            throw new RuntimeException(sprintf('wp_update_post(%d) refused the Divi layout: %s', $postId, $message));
+        }
+
+        DiviFlags::set($postId);
+
+        $stored = get_post($postId);
+
+        return $stored instanceof WP_Post && (string) $stored->post_content !== $content ? [self::CHANGED_ON_SAVE] : [];
+    }
+
     /**
      * Runs $write with kses' filters off for users without unfiltered_html (D7); restored in
      * finally, right when $write returns or throws.