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/psr/cache/README.md

@@ -0,0 +1,12 @@
+Caching Interface
+==============
+
+This repository holds all interfaces related to [PSR-6 (Caching Interface)][psr-url].
+
+Note that this is not a Caching implementation of its own. It is merely interfaces that describe the components of a Caching mechanism.
+
+The installable [package][package-url] and [implementations][implementation-url] are listed on Packagist.
+
+[psr-url]: https://www.php-fig.org/psr/psr-6/
+[package-url]: https://packagist.org/packages/psr/cache
+[implementation-url]: https://packagist.org/providers/psr/cache-implementation