refactor: one logging helper LIT\MCP\Log (M6)

Log::failure(context, detail) keeps the '[wp-lit-mcp] <context> failed: <detail>'
format of the nine former error_log() sites; Log::line() covers the change log line.
One phpcs ignore instead of eleven.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/Integrations/Divi/Pages/DiviPageLoader.php

@@ -10,6 +10,7 @@ use LIT\MCP\Integrations\Divi\BlockTree\NodeIndex;
 use LIT\MCP\Integrations\Divi\BlockTree\Parser;
 use LIT\MCP\Integrations\WordPress\PostGuard;
 use LIT\MCP\Integrations\WordPress\Schema\ContentSchema;
+use LIT\MCP\Log;
 use WP_Error;
 use WP_Post;
 
@@ -51,8 +52,7 @@ class DiviPageLoader
         try {
             $document = $this->parser->parse($content);
         } catch (MalformedMarkup $e) {
-            $message = sprintf('[wp-lit-mcp] divi parse of post %d failed: %s', $post->ID, $e->getMessage());
-            error_log($message); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
+            Log::failure(sprintf('divi parse of post %d', $post->ID), $e->getMessage());
 
             return Errors::unsupported(
                 sprintf(