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/html-sanitizer/Visitor/Node/NodeInterface.php

@@ -0,0 +1,37 @@
+<?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\HtmlSanitizer\Visitor\Node;
+
+/**
+ * Represents the sanitized version of a DOM node in the sanitized tree.
+ *
+ * Once the sanitization is done, nodes are rendered into the final output string.
+ *
+ * @author Titouan Galopin <galopintitouan@gmail.com>
+ */
+interface NodeInterface
+{
+    /**
+     * Add a child node to this node.
+     */
+    public function addChild(self $node): void;
+
+    /**
+     * Return the parent node of this node, or null if it has no parent node.
+     */
+    public function getParent(): ?self;
+
+    /**
+     * Render this node as a string, recursively rendering its children as well.
+     */
+    public function render(): string;
+}