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/webmozart/assert/src/InvalidArgumentException.php

@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the webmozart/assert package.
+ *
+ * (c) Bernhard Schussek <bschussek@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Webmozart\Assert;
+
+class InvalidArgumentException extends \InvalidArgumentException
+{
+}