refactor: DiviWriteAbility base and shared DiviErrors (H4)

The five Divi write tools extend DiviWriteAbility (final permission and
execute, change() per tool, shared output schema). DiviErrors holds the
unknown-node, position and compose-error mapping; DiviContentComposer uses
the same mapping (ledger T9). ToolNamingTest skips abstract classes.

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

src/Integrations/Divi/Pages/DiviContentComposer.php

@@ -98,9 +98,7 @@ final class DiviContentComposer implements ContentComposer
 
         $composed = $composition->composer()->compose(array_values($sections), null, 'divi');
         if ($composed['errors'] !== []) {
-            return $composed['invalid_paths'] !== []
-                ? Errors::invalidAttrPath($composed['errors'])
-                : Errors::invalidInput('Divi-Inhalt ist ungültig; nichts wurde angelegt.', $composed['errors']);
+            return DiviErrors::composed($composed, 'Divi-Inhalt ist ungültig; nichts wurde angelegt.');
         }
 
         $document = new Document();