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/http-message/README.md

@@ -0,0 +1,16 @@
+PSR Http Message
+================
+
+This repository holds all interfaces/classes/traits related to
+[PSR-7](http://www.php-fig.org/psr/psr-7/).
+
+Note that this is not a HTTP message implementation of its own. It is merely an
+interface that describes a HTTP message. See the specification for more details.
+
+Usage
+-----
+
+Before reading the usage guide we recommend reading the PSR-7 interfaces method list:
+
+* [`PSR-7 Interfaces Method List`](docs/PSR7-Interfaces.md)
+* [`PSR-7 Usage Guide`](docs/PSR7-Usage.md)