fix: DesignLock gegen parallele Bestätigungen; confirm ohne design_rev ist ein Eingabefehler

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

src/Integrations/Divi/Design/DesignLock.php

@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Integrations\Divi\Design;
+
+use InvalidArgumentException;
+
+defined('ABSPATH') || exit;
+
+/**
+ * One confirmed change per design area at a time (final review I-5): an option lit_mcp_lock_<area> (never
+ * autoloaded) holds the time the lock was taken. add_option() is atomic – it fails while the option exists. A lock
+ * older than STALE_AFTER seconds (a request that died) is removed and taken once more.
+ */
+final class DesignLock
+{
+    public const STALE_AFTER = 120;
+
+    private const PREFIX = 'lit_mcp_lock_';
+
+    /** @throws InvalidArgumentException For an area outside SnapshotStore::AREAS. */
+    public static function option(string $area): string
+    {
+        if (! in_array($area, SnapshotStore::AREAS, true)) {
+            throw new InvalidArgumentException(sprintf('Unknown design area "%s".', $area));
+        }
+
+        return self::PREFIX . $area;
+    }
+
+    public function acquire(string $area): bool
+    {
+        $option = self::option($area);
+        if (add_option($option, time(), '', false)) {
+            return true;
+        }
+
+        $since = get_option($option, 0);
+        if (is_numeric($since) && time() - (int) $since <= self::STALE_AFTER) {
+            return false;
+        }
+        delete_option($option);
+
+        return add_option($option, time(), '', false);
+    }
+
+    public function release(string $area): void
+    {
+        delete_option(self::option($area));
+    }
+}