Release v7.56.1

Added

• The agent worker result contract is published as a JSON Schema, a sample payload and a checker under Source/AgentHarnesses/contracts, so the harness and Studio test against the same artifact. (#711)

Fixed

• The agent harness always delivers a result Studio accepts: non-string gaps and selfChecks items written by the agent are converted to text, nulls are dropped, long text and long lists are capped to Studio's limits, and verbose advisory metadata is trimmed to fit with a marker saying how much was dropped. Usage and correlation values are forwarded byte for byte. (#711)
• A result that still cannot meet Studio's contract fails the worker with the clause it breaks, instead of being rejected by Studio without a reason. (#711)