fix(changelog): remove incorrect v0.1.4 slash command entry

The CHANGELOG incorrectly listed /status, /cost, and /version as new in v0.1.4.
These commands already existed in previous versions; PR #3333 only attempted to
add duplicate handlers (which was reverted in PR #3336). Remove the false claim.

CHANGELOG.md

@@ -13,7 +13,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - GJC-compatible `:conflicts` selector for git merge conflict detection
 - SDK wire transport with WebSocket support
 - Nix flake development environment
-- `/status`, `/cost`, and `/version` slash commands
 - Persistent provider configuration loading
 - Pagination support for large read_file results
 - Comprehensive GJC compatibility documentation and analysis