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/phpunit/php-invoker/README.md

@@ -0,0 +1,18 @@
+# phpunit/php-invoker
+
+[![CI Status](https://github.com/sebastianbergmann/php-invoker/workflows/CI/badge.svg)](https://github.com/sebastianbergmann/php-invoker/actions)
+[![Type Coverage](https://shepherd.dev/github/sebastianbergmann/php-invoker/coverage.svg)](https://shepherd.dev/github/sebastianbergmann/php-invoker)
+
+## Installation
+
+You can add this library as a local, per-project dependency to your project using [Composer](https://getcomposer.org/):
+
+```
+composer require phpunit/php-invoker
+```
+
+If you only need this library during development, for instance to run your project's test suite, then you should add it as a development-time dependency:
+
+```
+composer require --dev phpunit/php-invoker
+```