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/league/uri/UriTemplate/TemplateCanNotBeExpanded.php

@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * League.Uri (https://uri.thephpleague.com)
+ *
+ * (c) Ignace Nyamagana Butera <nyamsprod@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace League\Uri\UriTemplate;
+
+use InvalidArgumentException;
+use League\Uri\Contracts\UriException;
+
+class TemplateCanNotBeExpanded extends InvalidArgumentException implements UriException
+{
+    public readonly array $variablesNames;
+
+    public function __construct(string $message = '', string ...$variableNames)
+    {
+        parent::__construct($message, 0, null);
+
+        $this->variablesNames = $variableNames;
+    }
+
+    public static function dueToUnableToProcessValueListWithPrefix(string $variableName): self
+    {
+        return new self('The ":" modifier cannot be applied on "'.$variableName.'" since it is a list of values.', $variableName);
+    }
+
+    public static function dueToNestedListOfValue(string $variableName): self
+    {
+        return new self('The "'.$variableName.'" cannot be a nested list.', $variableName);
+    }
+
+    public static function dueToMissingVariables(string ...$variableNames): self
+    {
+        return new self('The following required variables are missing: `'.implode('`, `', $variableNames).'`.', ...$variableNames);
+    }
+}