📝 Note the duplicate-tag tests in the changelog

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- pin the duplicate-tag union collapse (members sharing a tag dispatch through
+  one handler) with tests
+- track a TypeScript 5.0 baseline in the backlog
+
 ## [0.8.0] - 2026-09-23
 
 - reject a universe that mixes a literal with a broad type (e.g.