refactor(compat): Capability-Interface, DiviFeature implementiert es

Grundlage der generischen Kompatibilitätsschicht für Fremd-Plugins mit inoffiziellen Schnittstellen (Plan docs/superpowers/plans/2026-11-06-kompatibilitaetsschicht.md).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/Compatibility/Capability.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Compatibility;
+
+defined('ABSPATH') || exit;
+
+/**
+ * One capability of an integration that a third-party plugin update may break separately. id() is unique across all
+ * integrations, so a bare ID is enough to find its capability.
+ */
+interface Capability
+{
+    /** Stable, globally unique ID such as 'page-read' or 'pods-field-write'. */
+    public function id(): string;
+
+    /** Name for messages and the admin tab (German). */
+    public function label(): string;
+
+    /** Whether the capability changes data. */
+    public function isWrite(): bool;
+}