fix: typed write failures, template rollback, parent and term cleanup

WriteFailed maps to lit_write_failed / lit_partial_write (partial writes are
logged with result partial); old template read before the update; row marker
set before wp_update_post; created terms deleted on rollback; parent must be a
readable non-descendant of a hierarchical type; featured image must be
readable; snapshot keeps empty values; meta comparison after sanitize_meta;
follow-up failures (listener, change log) only add warnings.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

tests/Unit/Integrations/WordPress/Schema/TermAssignerTest.php

@@ -69,7 +69,33 @@ final class TermAssignerTest extends TestCase
         Functions\expect('wp_insert_term')->once()->with('Neu', 'category')->andReturn(['term_id' => 15]);
         Functions\expect('wp_set_object_terms')->once()->with(5, [4, 15], 'category', false)->andReturn([4, 15]);
 
-        (new TermAssigner())->assign(5, ['category' => [4, 'Neu']]);
+        self::assertSame([15 => 'category'], (new TermAssigner())->assign(5, ['category' => [4, 'Neu']]));
+    }
+
+    public function testAFailedAssignmentDeletesTheTermsItCreated(): void
+    {
+        Functions\when('wp_insert_term')->justReturn(['term_id' => 15]);
+        Functions\when('wp_set_object_terms')->justReturn(new WP_Error('x', 'kaputt'));
+        Functions\expect('wp_delete_term')->once()->with(15, 'category')->andReturn(true);
+
+        $this->expectException(RuntimeException::class);
+
+        (new TermAssigner())->assign(5, ['category' => ['Neu']]);
+    }
+
+    public function testDeleteTermsAcceptsAlreadyMissingTermsAndThrowsOnRealFailures(): void
+    {
+        Functions\when('wp_delete_term')->alias(static fn (int $id): mixed => match ($id) {
+            15 => true,
+            16 => false,
+            default => new WP_Error('x', 'kaputt'),
+        });
+        $assigner = new TermAssigner();
+
+        $assigner->deleteTerms([15 => 'category', 16 => 'category']);
+
+        $this->expectException(RuntimeException::class);
+        $assigner->deleteTerms([15 => 'category', 17 => 'post_tag']);
     }
 
     public function testAssignFailureThrows(): void