ArtifactRevisionHashService (deterministic SHA-256 of the per-site
DeployArtifactsCommand, DeploymentId/timestamp excluded) stamps
Site.ArtifactRevisionHash/ArtifactsDeployedAt for every site whose deploy
succeeded; failed sites keep their previous stamp.
ComputeCurrentArtifactHashesAsync answers "what would it be now".
Claude-Session: https://claude.ai/code/session_01Y5ef34iUUMjmwnMpL9xgmB
Joseph Doherty