chore: add changelog entry for global AI assistant (#4532)

Author: elias-ba

CHANGELOG.md

@@ -18,6 +18,8 @@ and this project adheres to
 ### Added
 
 - AI assistant responses now stream in real-time
+- Add experimental global AI assistant option for users with experimental
+  features enabled [#4532](https://github.com/OpenFn/lightning/issues/4532)
   [#4517](https://github.com/OpenFn/lightning/pull/4517)
 
 ### Changed