docs(kafka): note that Go now reads envelope keys exactly

Author: muhammetsafak

packages/kafka/CHANGELOG.md

@@ -9,6 +9,10 @@ The envelope wire format is versioned separately by `meta.schema_version`
 
 ## [Unreleased]
 
+### Changed
+
+- Docs only: the note in the previous release that the Go reference's case-insensitive envelope-key read "is tightened separately" is now closed — Go core 1.14.0 reads envelope keys exactly (case-sensitive, last duplicate wins), so every SDK now decides poison on the same exact-case keys.
+
 ## [1.3.0] - 2026-10-12
 
 ### Changed