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/Output/BufferedOutput.php

@@ -0,0 +1,43 @@
+<?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\Output;
+
+/**
+ * @author Jean-François Simon <contact@jfsimon.fr>
+ */
+class BufferedOutput extends Output
+{
+    private string $buffer = '';
+
+    /**
+     * Empties buffer and returns its content.
+     */
+    public function fetch(): string
+    {
+        $content = $this->buffer;
+        $this->buffer = '';
+
+        return $content;
+    }
+
+    /**
+     * @return void
+     */
+    protected function doWrite(string $message, bool $newline)
+    {
+        $this->buffer .= $message;
+
+        if ($newline) {
+            $this->buffer .= \PHP_EOL;
+        }
+    }
+}