refactor: Cleanup git state - commit all staged changes

Major refactoring cleanup:
- Add new controller architecture (class-controller-*.php)
- Add new settings-v2 UI (views/settings-v2/)
- Add new CSS architecture (agentic-sidebar.css, tokens)
- Add esbuild build pipeline (scripts/build.js, package.json)
- Add composer dependencies (vendor/)
- Add frontend src directory (assets/js/src/index.jsx)
- Add documentation files
- Remove old/obsolete files (class-settings.php, old CSS)

This commits all pending changes from previous refactoring efforts.

vendor/symfony/config/ResourceCheckerInterface.php

@@ -0,0 +1,45 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Config;
+
+use Symfony\Component\Config\Resource\ResourceInterface;
+
+/**
+ * Interface for ResourceCheckers.
+ *
+ * When a ResourceCheckerConfigCache instance is checked for freshness, all its associated
+ * metadata resources are passed to ResourceCheckers. The ResourceCheckers
+ * can then inspect the resources and decide whether the cache can be considered
+ * fresh or not.
+ *
+ * @author Matthias Pigulla <mp@webfactory.de>
+ * @author Benjamin Klotz <bk@webfactory.de>
+ */
+interface ResourceCheckerInterface
+{
+    /**
+     * Queries the ResourceChecker whether it can validate a given
+     * resource or not.
+     *
+     * @return bool
+     */
+    public function supports(ResourceInterface $metadata);
+
+    /**
+     * Validates the resource.
+     *
+     * @param int $timestamp The timestamp at which the cache associated with this resource was created
+     *
+     * @return bool
+     */
+    public function isFresh(ResourceInterface $resource, int $timestamp);
+}