Update an actor.Include at least one of: description, risk_level, tags, nebulock_tags,groups, user_identifier, or escalated_till.description: Omit the key or send JSON null to leave unchanged; send "" to clear.Automated agents use the description when reasoning about this actor's correlated content.risk_level: One of high, low, or escalated. Omit, null, or "" to leaveunchanged. Agents use risk level together with the description to prioritize handling.When setting escalated, provide a future escalated_till (UTC).