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/src/Expression/expression.php

@@ -0,0 +1,159 @@
+<?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.
+ */
+
+namespace Parsica\Parsica\Expression;
+
+use Parsica\Parsica\Internal\Assert;
+use Parsica\Parsica\Parser;
+use function Parsica\Parsica\Internal\FP\foldl;
+
+/**
+ * Build an expression parser from a term parser and an expression table.
+ *
+ * @api
+ *
+ * @template TTerm
+ * @template TExpressionAST
+ *
+ * @psalm-param Parser<TTerm> $term
+ * @psalm-param list<ExpressionType> $expressionTable
+ *
+ * @psalm-return Parser<TExpressionAST>
+ * @psalm-pure
+ */
+function expression(Parser $term, array $expressionTable): Parser
+{
+    /**
+     * @psalm-var Parser<TExpressionAST> $parser
+     */
+    $parser = foldl(
+        $expressionTable,
+        fn(Parser $previous, ExpressionType $next) => $next->buildPrecedenceLevel($previous),
+        $term
+    );
+    return $parser;
+}
+
+/**
+ * A binary operator in an expression. The operands of the expression will be passed into $transform to produce the
+ * output of the expression parser.
+ *
+ * @api
+ *
+ * @template TSymbol
+ * @template TExpressionAST
+ * @psalm-param Parser<TSymbol> $symbol
+ * @psalm-param pure-callable(TExpressionAST, TExpressionAST):TExpressionAST $transform
+ * @psalm-param string $label
+ *
+ * @psalm-return BinaryOperator<TSymbol, TExpressionAST>
+ * @psalm-pure
+ */
+function binaryOperator(Parser $symbol, callable $transform, string $label = ""): BinaryOperator
+{
+    return new BinaryOperator($symbol, $transform, $label);
+}
+
+/**
+ * A unary operator in an expression. The operands of the expression will be passed into $transform to produce the
+ * output of the expression parser.
+ *
+ * @api
+ *
+ * @template TSymbol
+ * @template TExpressionAST
+ * @psalm-param Parser<TSymbol> $symbol
+ * @psalm-param callable(TExpressionAST):TExpressionAST $transform
+ * @psalm-param string $label
+ *
+ * @return UnaryOperator<TSymbol, TExpressionAST>
+ * @psalm-pure
+ */
+function unaryOperator(Parser $symbol, callable $transform, string $label = ""): UnaryOperator
+{
+    return new UnaryOperator($symbol, $transform, $label);
+}
+
+/**
+ * @api
+ * @template TSymbol
+ * @template TExpressionAST
+ * @psalm-param non-empty-list<BinaryOperator<TSymbol, TExpressionAST>> $operators
+ * @psalm-return LeftAssoc<TSymbol, TExpressionAST>
+ * @psalm-pure
+ */
+function leftAssoc(BinaryOperator ...$operators): LeftAssoc
+{
+    /** @psalm-suppress ImpureMethodCall */
+    Assert::nonEmptyList($operators, "LeftAssoc expects at least one Operator");
+    return new LeftAssoc($operators);
+}
+
+/**
+ * @api
+ * @template TSymbol
+ * @template TExpressionAST
+ * @psalm-param non-empty-list<BinaryOperator<TSymbol,TExpressionAST>> $operators
+ * @psalm-return RightAssoc<TSymbol, TExpressionAST>
+ * @psalm-pure
+ */
+function rightAssoc(BinaryOperator ...$operators): RightAssoc
+{
+    /** @psalm-suppress ImpureMethodCall */
+    Assert::nonEmptyList($operators, "RightAssoc expects at least one Operator");
+    return new RightAssoc($operators);
+}
+
+/**
+ * @api
+ *
+ * @template TSymbol
+ * @template TExpressionAST
+ * @psalm-param BinaryOperator<TSymbol, TExpressionAST> $operator
+ * @psalm-return NonAssoc<TSymbol, TExpressionAST>
+ * @psalm-pure
+ */
+function nonAssoc(BinaryOperator $operator): NonAssoc
+{
+    return new NonAssoc($operator);
+}
+
+/**
+ * @api
+ *
+ * @template TSymbol
+ * @template TExpressionAST
+ *
+ * @psalm-param non-empty-list<UnaryOperator<TSymbol, TExpressionAST>> $operators
+ * @psalm-return Prefix<TSymbol, TExpressionAST>
+ * @psalm-pure
+ */
+function prefix(UnaryOperator ...$operators): Prefix
+{
+    /** @psalm-suppress ImpureMethodCall */
+    Assert::nonEmptyList($operators, "Prefix expects at least one Operator");
+    return new Prefix($operators);
+}
+
+/**
+ * @api
+ *
+ * @template TSymbol
+ * @template TExpressionAST
+ * @psalm-param non-empty-list<UnaryOperator<TSymbol, TExpressionAST>> $operators
+ * @psalm-return Postfix<TSymbol, TExpressionAST>
+ * @psalm-pure
+ */
+function postfix(UnaryOperator ...$operators): Postfix
+{
+    /** @psalm-suppress ImpureMethodCall */
+    Assert::nonEmptyList($operators, "Postfix expects at least one Operator");
+    return new Postfix($operators);
+}