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/process/Exception/ProcessFailedException.php

@@ -0,0 +1,57 @@
+<?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\Process\Exception;
+
+use Symfony\Component\Process\Process;
+
+/**
+ * Exception for failed processes.
+ *
+ * @author Johannes M. Schmitt <schmittjoh@gmail.com>
+ */
+class ProcessFailedException extends RuntimeException
+{
+    private Process $process;
+
+    public function __construct(Process $process)
+    {
+        if ($process->isSuccessful()) {
+            throw new InvalidArgumentException('Expected a failed process, but the given process was successful.');
+        }
+
+        $error = \sprintf('The command "%s" failed.'."\n\nExit Code: %s(%s)\n\nWorking directory: %s",
+            $process->getCommandLine(),
+            $process->getExitCode(),
+            $process->getExitCodeText(),
+            $process->getWorkingDirectory()
+        );
+
+        if (!$process->isOutputDisabled()) {
+            $error .= \sprintf("\n\nOutput:\n================\n%s\n\nError Output:\n================\n%s",
+                $process->getOutput(),
+                $process->getErrorOutput()
+            );
+        }
+
+        parent::__construct($error);
+
+        $this->process = $process;
+    }
+
+    /**
+     * @return Process
+     */
+    public function getProcess()
+    {
+        return $this->process;
+    }
+}