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/parsica-php/parsica/docs/expressions.php

@@ -0,0 +1,36 @@
+<?php declare(strict_types=1);
+/**
+ * This file is part of the Parsica library.
+ *
+ * Copyright (c) 2020 Mathias Verraes <mathias@verraes.net>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/** @noinspection ALL */
+
+namespace Docs;
+
+// This code is executed by UpToDocs before each code block
+require_once __DIR__ . '/../vendor/autoload.php';
+
+
+use Parsica\Parsica\Parser;
+use function Parsica\Parsica\Expression\{binaryOperator,
+    expression,
+    leftAssoc,
+    postfix,
+    prefix,
+    rightAssoc,
+    unaryOperator};
+use function Parsica\Parsica\{atLeastOne, between, char, choice, digitChar, keepFirst, recursive, skipHSpace, string, alphaChar};
+use function PHPUnit\Framework\{assertSame, assertEquals};
+
+assert_options(ASSERT_ACTIVE, 1);
+
+
+$token = fn(Parser $parser) => keepFirst($parser, skipHSpace());
+$term = fn(): Parser => $token(atLeastOne(digitChar()))->map('intval');
+$parens = fn (Parser $parser): Parser =>  $token(between($token(char('(')), $token(char(')')), $parser));
+