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/Abilities/AbilityRegistrarTest.php

@@ -7,6 +7,7 @@ namespace LIT\MCP\Tests\Unit\Abilities;
 use Brain\Monkey\Functions;
 use LIT\MCP\Abilities\Ability;
 use LIT\MCP\Abilities\AbilityRegistrar;
+use LIT\MCP\Abilities\WriteFailed;
 use LIT\MCP\Integrations\Integration;
 use LIT\MCP\Integrations\IntegrationRegistry;
 use LIT\MCP\Server\RequestContext;
@@ -156,6 +157,27 @@ final class AbilityRegistrarTest extends TestCase
         unlink($log);
     }
 
+    public function testWriteFailedBecomesItsOwnErrorAndTheDetailIsLogged(): void
+    {
+        $log = (string) tempnam(sys_get_temp_dir(), 'lit-mcp-log');
+        $previous = ini_set('error_log', $log);
+        $ability = $this->ability();
+        $ability->expects('execute')->andThrow(
+            new WriteFailed('Felder konnten nicht gespeichert werden.', false, 5, 811, new RuntimeException('meta /var/www'))
+        );
+
+        try {
+            $result = ($this->registrarFor($ability)->argsFor($ability)['execute_callback'])([]);
+        } finally {
+            ini_set('error_log', (string) $previous);
+        }
+
+        self::assertSame('lit_partial_write', $result->get_error_code());
+        self::assertStringNotContainsString('/var/www', $result->get_error_message());
+        self::assertStringContainsString('meta /var/www', (string) file_get_contents($log));
+        unlink($log);
+    }
+
     public function testRegisterAbilitiesCallsWordPressForEachAbility(): void
     {
         $ability = $this->ability();