Changelog and deprecation policy

Documentation changes ship with the code or configuration they describe. Each externally visible API or contract change records its release, migration requirement, and rollback path.

• Additive API changes remain within the current version when old consumers continue to work.
• Breaking API changes require a new version and a published overlap window.
• Contract, oracle, and deployment-registry changes link to their governance evidence.
• Removed surfaces remain documented as deprecated for at least one supported release.
• Claims about liquidity, yield, redemption, custody, or decentralization require verified evidence.