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

src/Dependencies.php

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP;
+
+/**
+ * Checks that the libraries WP-LIT-MCP builds on are loadable.
+ */
+final class Dependencies
+{
+    private const REQUIRED = [
+        'wordpress/mcp-adapter' => 'WP\\MCP\\Core\\McpAdapter',
+        'wp-media/mcp-oauth' => 'WPMedia\\MCP\\OAuth\\Bootstrap',
+        'WordPress Abilities API' => 'WP_Ability',
+    ];
+
+    /** @var callable(string): bool */
+    private $classExists;
+
+    public function __construct(?callable $classExists = null)
+    {
+        $this->classExists = $classExists ?? static fn (string $class): bool => class_exists($class);
+    }
+
+    /**
+     * @return list<string> Human-readable names of missing components.
+     */
+    public function missing(): array
+    {
+        $missing = [];
+        foreach (self::REQUIRED as $name => $class) {
+            if (! ($this->classExists)($class)) {
+                $missing[] = $name;
+            }
+        }
+
+        return $missing;
+    }
+}

src/Plugin.php

@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP;
+
+/**
+ * Wires WP-LIT-MCP into WordPress.
+ */
+final class Plugin
+{
+    private static string $pluginFile = '';
+
+    public static function boot(string $pluginFile): void
+    {
+        self::$pluginFile = $pluginFile;
+
+        $missing = (new Dependencies())->missing();
+        if ($missing !== []) {
+            self::noticeMissing($missing);
+            return;
+        }
+    }
+
+    public static function pluginDir(): string
+    {
+        return dirname(self::$pluginFile);
+    }
+
+    /**
+     * @param list<string> $missing
+     */
+    public static function noticeMissing(array $missing): void
+    {
+        add_action('admin_notices', static function () use ($missing): void {
+            printf(
+                '<div class="notice notice-error"><p>%s</p></div>',
+                esc_html(sprintf(
+                    /* translators: %s: comma separated list of missing components */
+                    __('WP-LIT-MCP ist inaktiv. Es fehlt: %s', 'wp-lit-mcp'),
+                    implode(', ', $missing)
+                ))
+            );
+        });
+    }
+}