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/phpunit/php-invoker/src/Invoker.php

@@ -0,0 +1,69 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-invoker.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace SebastianBergmann\Invoker;
+
+use const SIGALRM;
+use function call_user_func_array;
+use function function_exists;
+use function pcntl_alarm;
+use function pcntl_async_signals;
+use function pcntl_signal;
+use function sprintf;
+use Throwable;
+
+final class Invoker
+{
+    /**
+     * @var int
+     */
+    private $timeout;
+
+    /**
+     * @throws Throwable
+     */
+    public function invoke(callable $callable, array $arguments, int $timeout)
+    {
+        if (!$this->canInvokeWithTimeout()) {
+            throw new ProcessControlExtensionNotLoadedException(
+                'The pcntl (process control) extension for PHP is required'
+            );
+        }
+
+        pcntl_signal(
+            SIGALRM,
+            function (): void {
+                throw new TimeoutException(
+                    sprintf(
+                        'Execution aborted after %d second%s',
+                        $this->timeout,
+                        $this->timeout === 1 ? '' : 's'
+                    )
+                );
+            },
+            true
+        );
+
+        $this->timeout = $timeout;
+
+        pcntl_async_signals(true);
+        pcntl_alarm($timeout);
+
+        try {
+            return call_user_func_array($callable, $arguments);
+        } finally {
+            pcntl_alarm(0);
+        }
+    }
+
+    public function canInvokeWithTimeout(): bool
+    {
+        return function_exists('pcntl_signal') && function_exists('pcntl_async_signals') && function_exists('pcntl_alarm');
+    }
+}