Scenario Replication Started
data class ScenarioReplicationStarted(val scenarioName: String, val repNumber: Int, val totalReplications: Int) : RunEvent(source)
Emitted by ScenarioOrchestrator immediately before scenario scenarioName begins replication repNumber. Carries the same payload as ReplicationStarted but tagged with the scenario name, so multi-scenario consumers (the Scenario app's GUI in particular) can attribute per-replication progress to the right row.