Note GPL-3.0 relicense in changelog

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: rbibby53

CHANGELOG.md

@@ -22,6 +22,7 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 ### Changed
 - Requires Java 26.
 - Default behavior is now run-until-stopped instead of a fixed 4000 cycles.
+- Relicensed from MIT to GPL-3.0.
 
 ### Fixed
 - Filename case mismatch that broke playback on case-sensitive filesystems.