chore: update native error changeset

Document the separate nativeError debug field without suggesting native details belong in user-facing messages.

Author: bryceknz

.changeset/fuzzy-ravens-explain.md

@@ -2,4 +2,4 @@
 "react-native-app-auth": patch
 ---
 
-Include underlying native error causes in Android and iOS authorization error messages.
+Expose underlying native authorization errors on `error.nativeError` for debugging while keeping `error.message` user-safe.