fix: lit/library-list search by title, own entries for authors, cursor without hidden rows (L3)

search uses search_columns post_title; users without edit_others_posts on
et_pb_layout query their own entries only (PostGuard::ownPostsOnly); the
cursor counts the entries shown, never the rows left out.

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

tests/Unit/Integrations/Divi/Library/DiviLibraryStoreTest.php

@@ -86,6 +86,8 @@ final class DiviLibraryStoreTest extends TestCase
         self::assertSame(21, $captured['posts_per_page']);
         self::assertSame(40, $captured['offset']);
         self::assertSame('Kopf', $captured['s']);
+        self::assertSame(['post_title'], $captured['search_columns'], 'audit L3: the title only');
+        self::assertArrayNotHasKey('author', $captured);
         self::assertSame(
             [
                 'relation' => 'AND',
@@ -97,6 +99,21 @@ final class DiviLibraryStoreTest extends TestCase
         );
     }
 
+    /** Audit L3: users without edit_others_posts query their own entries only. */
+    public function testFindRestrictsToAnAuthor(): void
+    {
+        $captured = [];
+        Functions\when('get_posts')->alias(static function (array $args) use (&$captured): array {
+            $captured = $args;
+
+            return [];
+        });
+
+        (new DiviLibraryStore())->find(['author' => 12], 20, 0);
+
+        self::assertSame(12, $captured['author']);
+    }
+
     public function testReportsMissingTaxonomies(): void
     {
         Functions\when('taxonomy_exists')->alias(static fn (string $taxonomy): bool => $taxonomy !== 'scope');