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/PostPublishAbilityTest.php

@@ -36,7 +36,7 @@ final class PostPublishAbilityTest extends TestCase
         Functions\expect('wp_update_post')->once()->with(['ID' => 5, 'post_status' => 'publish'], true)->andReturn(5);
         Functions\when('get_post_status')->justReturn('publish');
         $log = Mockery::mock(ChangeLog::class);
-        $log->expects('record')->with('lit/post-publish', 'page', '5', '"Team" veröffentlicht')->andReturn(9);
+        $log->expects('record')->with('lit/post-publish', 'page', '5', '"Team" veröffentlicht', null)->andReturn(9);
 
         $result = $this->ability($log)->execute(['post_id' => 5]);