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/CHANGELOG.md

@@ -0,0 +1,36 @@
+# Changelog
+
+All notable changes to this project will be documented in this file, in reverse chronological order by release.
+
+## 1.0.1 - 2016-08-06
+
+### Added
+
+- Nothing.
+
+### Deprecated
+
+- Nothing.
+
+### Removed
+
+- Nothing.
+
+### Fixed
+
+- Updated all `@return self` annotation references in interfaces to use
+  `@return static`, which more closelly follows the semantics of the
+  specification.
+- Updated the `MessageInterface::getHeaders()` return annotation to use the
+  value `string[][]`, indicating the format is a nested array of strings.
+- Updated the `@link` annotation for `RequestInterface::withRequestTarget()`
+  to point to the correct section of RFC 7230.
+- Updated the `ServerRequestInterface::withUploadedFiles()` parameter annotation
+  to add the parameter name (`$uploadedFiles`).
+- Updated a `@throws` annotation for the `UploadedFileInterface::moveTo()`
+  method to correctly reference the method parameter (it was referencing an
+  incorrect parameter name previously).
+
+## 1.0.0 - 2016-05-18
+
+Initial stable release; reflects accepted PSR-7 specification.