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/DiviReplaceTextAbility.php

@@ -15,6 +15,7 @@ use LIT\MCP\Integrations\Divi\BlockTree\Serializer;
 use LIT\MCP\Integrations\Divi\Compose\TextReplacer;
 use LIT\MCP\Integrations\WordPress\PostGuard;
 use LIT\MCP\Integrations\WordPress\Schema\ContentSchema;
+use LIT\MCP\Log;
 use Throwable;
 use WP_Error;
 
@@ -484,8 +485,7 @@ final class DiviReplaceTextAbility implements Ability
 
     private static function log(int $postId, Throwable $e): void
     {
-        $message = sprintf('[wp-lit-mcp] lit/divi-replace-text on post %d failed: %s', $postId, $e);
-        error_log($message); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
+        Log::failure(sprintf('lit/divi-replace-text on post %d', $postId), $e);
     }
 
     private function db(): \wpdb