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/http-client/Response/JsonMockResponse.php

@@ -0,0 +1,47 @@
+<?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\HttpClient\Response;
+
+use Symfony\Component\HttpClient\Exception\InvalidArgumentException;
+
+class JsonMockResponse extends MockResponse
+{
+    /**
+     * @param mixed $body Any value that `json_encode()` can serialize
+     */
+    public function __construct(mixed $body = [], array $info = [])
+    {
+        try {
+            $json = json_encode($body, \JSON_THROW_ON_ERROR | \JSON_PRESERVE_ZERO_FRACTION);
+        } catch (\JsonException $e) {
+            throw new InvalidArgumentException('JSON encoding failed: '.$e->getMessage(), $e->getCode(), $e);
+        }
+
+        $info['response_headers']['content-type'] ??= 'application/json';
+
+        parent::__construct($json, $info);
+    }
+
+    public static function fromFile(string $path, array $info = []): static
+    {
+        if (!is_file($path)) {
+            throw new InvalidArgumentException(\sprintf('File not found: "%s".', $path));
+        }
+
+        $json = file_get_contents($path);
+        if (!json_validate($json)) {
+            throw new \InvalidArgumentException(\sprintf('File "%s" does not contain valid JSON.', $path));
+        }
+
+        return new static(json_decode($json, true, flags: \JSON_THROW_ON_ERROR), $info);
+    }
+}