refactor: PostChangeResult for the after-save block of the post tools

after_save hook, re-read, change log and ToolResult (rev, log_id, warnings)
were repeated in nine post abilities; they now share one helper. Behaviour
and warning texts are unchanged.

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

tests/Unit/Integrations/WordPress/Status/PostTrashAbilityTest.php

@@ -38,7 +38,7 @@ final class PostTrashAbilityTest extends TestCase
         Functions\expect('wp_trash_post')->once()->with(5)->andReturn(new WP_Post(['ID' => 5]));
         Functions\expect('wp_delete_post')->never();
         $log = Mockery::mock(ChangeLog::class);
-        $log->expects('record')->with('lit/post-trash', 'page', '5', '"Alt" in den Papierkorb gelegt')->andReturn(2);
+        $log->expects('record')->with('lit/post-trash', 'page', '5', '"Alt" in den Papierkorb gelegt', null)->andReturn(2);
 
         $result = $this->ability($log)->execute(['post_id' => 5, 'confirm' => true]);