feat(tool): implement tool package support with validation and configuration

src/StaticPHP/Attribute/Package/Tool.php

@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace StaticPHP\Attribute\Package;
+
+/**
+ * Indicates that the annotated class defines a tool package.
+ */
+#[\Attribute(\Attribute::TARGET_CLASS | \Attribute::IS_REPEATABLE)]
+readonly class Tool
+{
+    public function __construct(public string $name) {}
+}