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/dependency-injection/Extension/ExtensionInterface.php

@@ -0,0 +1,56 @@
+<?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\DependencyInjection\Extension;
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+/**
+ * ExtensionInterface is the interface implemented by container extension classes.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+interface ExtensionInterface
+{
+    /**
+     * Loads a specific configuration.
+     *
+     * @param array<array<mixed>> $configs
+     *
+     * @return void
+     *
+     * @throws \InvalidArgumentException When provided tag is not defined in this extension
+     */
+    public function load(array $configs, ContainerBuilder $container);
+
+    /**
+     * Returns the namespace to be used for this extension (XML namespace).
+     *
+     * @return string
+     */
+    public function getNamespace();
+
+    /**
+     * Returns the base path for the XSD files.
+     *
+     * @return string|false
+     */
+    public function getXsdValidationBasePath();
+
+    /**
+     * Returns the recommended alias to use in XML.
+     *
+     * This alias is also the mandatory prefix to use when using YAML.
+     *
+     * @return string
+     */
+    public function getAlias();
+}