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/yaml/ParserState.php

@@ -0,0 +1,69 @@
+<?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\Yaml;
+
+use Symfony\Component\Yaml\Exception\ParseException;
+use Symfony\Component\Yaml\Tag\TaggedValue;
+
+/**
+ * @internal
+ */
+final class ParserState
+{
+    public int $maxNestingLevel = Parser::DEFAULT_MAX_NESTING_LEVEL;
+    public int $currentNestingLevel = 0;
+    public int $maxAliasesForCollections = Parser::DEFAULT_MAX_ALIASES_FOR_COLLECTIONS;
+    public int $collectionAliasCount = 0;
+    public bool $aliasesEnabled = true;
+
+    public function reset(): void
+    {
+        $this->currentNestingLevel = 0;
+        $this->collectionAliasCount = 0;
+        $this->aliasesEnabled = true;
+    }
+
+    public function enterNestingLevel(int $line, ?string $snippet, ?string $filename): void
+    {
+        if (++$this->currentNestingLevel > $this->maxNestingLevel) {
+            --$this->currentNestingLevel;
+
+            throw new ParseException(\sprintf('Maximum nesting depth of %d exceeded.', $this->maxNestingLevel), $line, $snippet, $filename);
+        }
+    }
+
+    public function leaveNestingLevel(): void
+    {
+        if ($this->currentNestingLevel > 0) {
+            --$this->currentNestingLevel;
+        }
+    }
+
+    public function countAlias(mixed $refValue, int $line, ?string $snippet, ?string $filename): void
+    {
+        if (!$this->aliasesEnabled) {
+            throw new ParseException('Aliases are disabled.', $line, $snippet, $filename);
+        }
+
+        if ($refValue instanceof TaggedValue) {
+            $refValue = $refValue->getValue();
+        }
+
+        if (!\is_array($refValue) && !$refValue instanceof \stdClass) {
+            return;
+        }
+
+        if (++$this->collectionAliasCount > $this->maxAliasesForCollections) {
+            throw new ParseException(\sprintf('Maximum number of collection aliases (%d) exceeded. This limit can be increased via the Parser constructor.', $this->maxAliasesForCollections), $line, $snippet, $filename);
+        }
+    }
+}