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/polyfill-php80/bootstrap.php

@@ -0,0 +1,42 @@
+<?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.
+ */
+
+use Symfony\Polyfill\Php80 as p;
+
+if (\PHP_VERSION_ID >= 80000) {
+    return;
+}
+
+if (!defined('FILTER_VALIDATE_BOOL') && defined('FILTER_VALIDATE_BOOLEAN')) {
+    define('FILTER_VALIDATE_BOOL', \FILTER_VALIDATE_BOOLEAN);
+}
+
+if (!function_exists('fdiv')) {
+    function fdiv(float $num1, float $num2): float { return p\Php80::fdiv($num1, $num2); }
+}
+if (!function_exists('preg_last_error_msg')) {
+    function preg_last_error_msg(): string { return p\Php80::preg_last_error_msg(); }
+}
+if (!function_exists('str_contains')) {
+    function str_contains(?string $haystack, ?string $needle): bool { return p\Php80::str_contains($haystack ?? '', $needle ?? ''); }
+}
+if (!function_exists('str_starts_with')) {
+    function str_starts_with(?string $haystack, ?string $needle): bool { return p\Php80::str_starts_with($haystack ?? '', $needle ?? ''); }
+}
+if (!function_exists('str_ends_with')) {
+    function str_ends_with(?string $haystack, ?string $needle): bool { return p\Php80::str_ends_with($haystack ?? '', $needle ?? ''); }
+}
+if (!function_exists('get_debug_type')) {
+    function get_debug_type($value): string { return p\Php80::get_debug_type($value); }
+}
+if (!function_exists('get_resource_id')) {
+    function get_resource_id($resource): int { return p\Php80::get_resource_id($resource); }
+}