docs: update changelog for grants query params fix

- Add unreleased section with fix for ListGrantsQueryParams.sortBy values
- Follows conventional commits format

Author: cursoragent

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+- Updated `ListGrantsQueryParams.sortBy` values to match API expectations (`'created_at' | 'updated_at'` instead of `'createdAt' | 'updatedAt'`)
+
 ## [7.13.1] - 2025-09-18
 
 ### Fixed