docs: update CHANGELOG for v2.1.1

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: 2 people

CHANGELOG.md

@@ -5,6 +5,16 @@ All notable changes to MyConvergio will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.1.1] - 2025-12-28
+
+### Added
+- `myconvergio agents` command to list all installed agents with versions and model tiers
+
+### Fixed
+- Postinstall now always creates backup if existing content found (not just if manifest exists)
+- Postinstall output now visible during npm install (uses stderr)
+- Consistent backup behavior between postinstall.js and CLI
+
 ## [2.1.0] - 2025-12-28
 
 ### Added