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/NullOutput.php

@@ -0,0 +1,104 @@
+<?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\Formatter\NullOutputFormatter;
+use Symfony\Component\Console\Formatter\OutputFormatterInterface;
+
+/**
+ * NullOutput suppresses all output.
+ *
+ *     $output = new NullOutput();
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ * @author Tobias Schultze <http://tobion.de>
+ */
+class NullOutput implements OutputInterface
+{
+    private NullOutputFormatter $formatter;
+
+    /**
+     * @return void
+     */
+    public function setFormatter(OutputFormatterInterface $formatter)
+    {
+        // do nothing
+    }
+
+    public function getFormatter(): OutputFormatterInterface
+    {
+        // to comply with the interface we must return a OutputFormatterInterface
+        return $this->formatter ??= new NullOutputFormatter();
+    }
+
+    /**
+     * @return void
+     */
+    public function setDecorated(bool $decorated)
+    {
+        // do nothing
+    }
+
+    public function isDecorated(): bool
+    {
+        return false;
+    }
+
+    /**
+     * @return void
+     */
+    public function setVerbosity(int $level)
+    {
+        // do nothing
+    }
+
+    public function getVerbosity(): int
+    {
+        return self::VERBOSITY_QUIET;
+    }
+
+    public function isQuiet(): bool
+    {
+        return true;
+    }
+
+    public function isVerbose(): bool
+    {
+        return false;
+    }
+
+    public function isVeryVerbose(): bool
+    {
+        return false;
+    }
+
+    public function isDebug(): bool
+    {
+        return false;
+    }
+
+    /**
+     * @return void
+     */
+    public function writeln(string|iterable $messages, int $options = self::OUTPUT_NORMAL)
+    {
+        // do nothing
+    }
+
+    /**
+     * @return void
+     */
+    public function write(string|iterable $messages, bool $newline = false, int $options = self::OUTPUT_NORMAL)
+    {
+        // do nothing
+    }
+}