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/TrimmedBufferOutput.php

@@ -0,0 +1,61 @@
+<?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;
+
+use Symfony\Component\Console\Exception\InvalidArgumentException;
+use Symfony\Component\Console\Formatter\OutputFormatterInterface;
+
+/**
+ * A BufferedOutput that keeps only the last N chars.
+ *
+ * @author Jérémy Derussé <jeremy@derusse.com>
+ */
+class TrimmedBufferOutput extends Output
+{
+    private int $maxLength;
+    private string $buffer = '';
+
+    public function __construct(int $maxLength, ?int $verbosity = self::VERBOSITY_NORMAL, bool $decorated = false, ?OutputFormatterInterface $formatter = null)
+    {
+        if ($maxLength <= 0) {
+            throw new InvalidArgumentException(\sprintf('"%s()" expects a strictly positive maxLength. Got %d.', __METHOD__, $maxLength));
+        }
+
+        parent::__construct($verbosity, $decorated, $formatter);
+        $this->maxLength = $maxLength;
+    }
+
+    /**
+     * 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;
+        }
+
+        $this->buffer = substr($this->buffer, 0 - $this->maxLength);
+    }
+}