docs: Update CHANGELOG for LICENSE simplification

Document the LICENSE simplification change in CHANGELOG to satisfy
version validation requirement.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kiyotis

.claude/skills/nabledge-6/plugin/CHANGELOG.md

@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Migrated to Claude Code marketplace distribution structure
 - Plugin now distributed via marketplace catalog (nablarch/nabledge)
 - Users should install via: `/plugin marketplace add nablarch/nabledge` then `/plugin install nabledge-6@nablarch-nabledge`
+- Simplified license management: single LICENSE at repository root applies to entire marketplace
 
 ## [0.1] - 2026-02-12