Add missing ConfigurationException and update PHPStan baseline (#31)

- Add ConfigurationException class in src/Exception/ConfigurationException.php
- Update ServerBuilder to use the new ConfigurationException
- Regenerate PHPStan baseline to account for the new exception class,
  reducing errors from 160+ to 124

src/Exception/ConfigurationException.php

@@ -0,0 +1,19 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Exception;
+
+/**
+ * @author Oskar Stark <oskarstark@googlemail.com>
+ */
+class ConfigurationException extends InvalidArgumentException
+{
+}

src/Server/ServerBuilder.php

@@ -21,6 +21,7 @@ use Mcp\Capability\Prompt\Completion\ListCompletionProvider;
 use Mcp\Capability\Registry;
 use Mcp\Capability\Registry\Container;
 use Mcp\Capability\Registry\ReferenceHandler;
+use Mcp\Exception\ConfigurationException;
 use Mcp\JsonRpc\Handler;
 use Mcp\Schema\Annotations;
 use Mcp\Schema\Implementation;