Define canonical validation_result contract #3

Job	Run time
contract-audit	1m 27s
smoke-runtime (baseline, configs/registry_smoke_matrix.json)	13m 53s
smoke-runtime (sg-only, configs/registry_smoke_matrix.json)	15m 2s
smoke-runtime (artifact-only, configs/registry_smoke_artifact_matrix.json)	12m 14s
	42m 36s

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