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/nikic/php-parser/lib/PhpParser/Node/InterpolatedStringPart.php

@@ -0,0 +1,32 @@
+<?php declare(strict_types=1);
+
+namespace PhpParser\Node;
+
+use PhpParser\NodeAbstract;
+
+class InterpolatedStringPart extends NodeAbstract {
+    /** @var string String value */
+    public string $value;
+
+    /**
+     * Constructs a node representing a string part of an interpolated string.
+     *
+     * @param string $value String value
+     * @param array<string, mixed> $attributes Additional attributes
+     */
+    public function __construct(string $value, array $attributes = []) {
+        $this->attributes = $attributes;
+        $this->value = $value;
+    }
+
+    public function getSubNodeNames(): array {
+        return ['value'];
+    }
+
+    public function getType(): string {
+        return 'InterpolatedStringPart';
+    }
+}
+
+// @deprecated compatibility alias
+class_alias(InterpolatedStringPart::class, Scalar\EncapsedStringPart::class);