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/Loader.php

@@ -0,0 +1,73 @@
+<?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;
+
+use Symfony\Component\Config\Exception\LoaderLoadException;
+
+/**
+ * Loader is the abstract class used by all built-in loaders.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+abstract class Loader implements LoaderInterface
+{
+    protected $resolver;
+    protected $env;
+
+    public function __construct(?string $env = null)
+    {
+        $this->env = $env;
+    }
+
+    public function getResolver(): LoaderResolverInterface
+    {
+        return $this->resolver;
+    }
+
+    /**
+     * @return void
+     */
+    public function setResolver(LoaderResolverInterface $resolver)
+    {
+        $this->resolver = $resolver;
+    }
+
+    /**
+     * Imports a resource.
+     *
+     * @return mixed
+     */
+    public function import(mixed $resource, ?string $type = null)
+    {
+        return $this->resolve($resource, $type)->load($resource, $type);
+    }
+
+    /**
+     * Finds a loader able to load an imported resource.
+     *
+     * @throws LoaderLoadException If no loader is found
+     */
+    public function resolve(mixed $resource, ?string $type = null): LoaderInterface
+    {
+        if ($this->supports($resource, $type)) {
+            return $this;
+        }
+
+        $loader = null === $this->resolver ? false : $this->resolver->resolve($resource, $type);
+
+        if (false === $loader) {
+            throw new LoaderLoadException($resource, null, 0, null, $type);
+        }
+
+        return $loader;
+    }
+}