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/console/SignalRegistry/SignalMap.php

@@ -0,0 +1,36 @@
+<?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\Console\SignalRegistry;
+
+/**
+ * @author Grégoire Pineau <lyrixx@lyrixx.info>
+ */
+class SignalMap
+{
+    private static array $map;
+
+    public static function getSignalName(int $signal): ?string
+    {
+        if (!\extension_loaded('pcntl')) {
+            return null;
+        }
+
+        if (!isset(self::$map)) {
+            $r = new \ReflectionExtension('pcntl');
+            $c = $r->getConstants();
+            $map = array_filter($c, static fn ($k) => str_starts_with($k, 'SIG') && !str_starts_with($k, 'SIG_') && 'SIGBABY' !== $k, \ARRAY_FILTER_USE_KEY);
+            self::$map = array_flip($map);
+        }
+
+        return self::$map[$signal] ?? null;
+    }
+}