feat: deferred 1a items - menu_rev lock, lit_mcp_guides filter, warnings, schedule guard precision

Task 14 (rulings P17/P18, Q10):
- lit/menu-get returns menu_rev (Rev::ofMenu over id, parent, position,
  title, url, object, object_id); lit/menu-set-items requires it, refuses
  a stale one with rev_mismatch (hint: lit/menu-get) and returns the new
  menu_rev. Errors::revMismatch takes an optional message/hint.
- GuideRepository: filter lit_mcp_guides adds/overrides topics; invalid
  topic names and non-string content are ignored, files stay the default.
- lit/post-trash names front page, posts page and linking menus in the
  confirmation and as warnings; lit/menu-assign-location needs confirm
  to remove an assigned menu and names it; lit/post-schedule warns that
  a private entry becomes public; Divi hints no longer point to
  non-existing lit-divi-* tools.
- PostGuard::missedSchedule: 60 s publish window, zero GMT date falls
  back to get_gmt_from_date(post_date); post-schedule refuses dates
  within that window.
- write_failed after a clean rollback that keeps a revision/backup says
  "Die Aenderung wurde nicht gespeichert (... bleibt erhalten)" via the
  new state parameter (Errors::writeFailed / WriteFailed rolledBackState).
- wp-basis-smoke: menu_rev flow, unassign confirm, trash/menu and
  private-schedule warnings.

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

tests/Unit/Abilities/ErrorsTest.php

@@ -67,6 +67,30 @@ final class ErrorsTest extends TestCase
         self::assertStringContainsString('erneut', $payload['hint']);
     }
 
+    public function testWriteFailedCanDescribeWhatWasKept(): void
+    {
+        $error = Errors::writeFailed(
+            'Felder konnten nicht gespeichert werden.',
+            [],
+            null,
+            'Die Änderung wurde nicht gespeichert (Revision 811 bleibt erhalten).'
+        );
+
+        $message = json_decode($error->get_error_message(), true)['message'];
+        self::assertStringNotContainsString('Nichts wurde gespeichert', $message);
+        self::assertStringEndsWith('Die Änderung wurde nicht gespeichert (Revision 811 bleibt erhalten).', $message);
+    }
+
+    public function testRevMismatchCanNameItsOwnObjectAndReadTool(): void
+    {
+        $error = Errors::revMismatch('Das Menü wurde geändert.', 'Mit lit/menu-get neu lesen.');
+
+        self::assertSame('lit_rev_mismatch', $error->get_error_code());
+        self::assertSame('Das Menü wurde geändert.', json_decode($error->get_error_message(), true)['message']);
+        self::assertSame('Mit lit/menu-get neu lesen.', $error->get_error_data()['hint']);
+        self::assertStringContainsString('lit/content-get', Errors::revMismatch()->get_error_data()['hint']);
+    }
+
     public function testPartialWriteNamesWhatMayHaveBeenSavedAndWarnsAgainstRetrying(): void
     {
         $error = Errors::partialWrite('Felder konnten nicht gespeichert werden.', 5, 811);