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/Loader/LoaderInterface.php

@@ -0,0 +1,52 @@
+<?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\Loader;
+
+/**
+ * LoaderInterface is the interface implemented by all loader classes.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+interface LoaderInterface
+{
+    /**
+     * Loads a resource.
+     *
+     * @return mixed
+     *
+     * @throws \Exception If something went wrong
+     */
+    public function load(mixed $resource, ?string $type = null);
+
+    /**
+     * Returns whether this class supports the given resource.
+     *
+     * @param mixed $resource A resource
+     *
+     * @return bool
+     */
+    public function supports(mixed $resource, ?string $type = null);
+
+    /**
+     * Gets the loader resolver.
+     *
+     * @return LoaderResolverInterface
+     */
+    public function getResolver();
+
+    /**
+     * Sets the loader resolver.
+     *
+     * @return void
+     */
+    public function setResolver(LoaderResolverInterface $resolver);
+}