feat: plugin scaffold with dependency check

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

tests/Stubs/WpError.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+if (! class_exists('WP_Error')) {
+    class WP_Error
+    {
+        public function __construct(
+            private string $code = '',
+            private string $message = '',
+            private mixed $data = null
+        ) {
+        }
+
+        public function get_error_code(): string
+        {
+            return $this->code;
+        }
+
+        public function get_error_message(): string
+        {
+            return $this->message;
+        }
+
+        public function get_error_data(): mixed
+        {
+            return $this->data;
+        }
+    }
+}

tests/Stubs/WpUser.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+if (! class_exists('WP_User')) {
+    class WP_User
+    {
+        public int $ID = 0;
+        public array $roles = [];
+
+        public function __construct(int $id = 0, array $roles = [])
+        {
+            $this->ID = $id;
+            $this->roles = $roles;
+        }
+    }
+}