docs: mark v0.5.2 as yanked in CHANGELOG

Author: ddunnock

CHANGELOG.md

@@ -13,7 +13,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed `acp constraints` → `acp check` in primer CLI overview section
 - Updated acp-spec submodule with corrected primer.defaults.json
 
-## [0.5.2] - 2025-12-30
+## [0.5.2] - 2025-12-30 [YANKED]
+
+Yanked due to `acp constraints` not being renamed to `acp check` in CLI overview.
 
 ### Fixed
 - Fixed crates.io packaging: primer.defaults.json now included via build.rs