Default Builder logger to NullLogger for silent programmatic use

The CLI command sets its own ConsoleLogger explicitly, so this only
affects programmatic usage where silent-by-default is preferred.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: DerManoMann

docs/reference/builder.md

@@ -44,7 +44,7 @@ Sets the target OpenAPI version. If not set, defaults to the version declared in
 $builder->setLogger($psrLogger);
 ```
 
-Accepts any PSR-3 logger. Defaults to `DefaultLogger` (which writes warnings to PHP's error log).
+Accepts any PSR-3 logger. Defaults to `NullLogger` (silent). The CLI command sets its own console logger.
 
 ### Generator configuration
 

src/Builder.php

@@ -8,9 +8,9 @@
 
 use OpenApi\Builder\CollectingLogger;
 use OpenApi\Builder\Result;
-use OpenApi\Loggers\DefaultLogger;
 use OpenApi\Utils\SourceScanner;
 use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
 
 /**
  * Unified entry point for generating OpenAPI specs.
@@ -80,7 +80,7 @@ public function build(): Result
 
     protected function getLogger(): LoggerInterface
     {
-        $this->logger ??= new DefaultLogger();
+        $this->logger ??= new NullLogger();
 
         return $this->logger;
     }