Scenario Started
data class ScenarioStarted(val scenarioName: String, val index: Int, val totalScenarios: Int) : RunEvent(source)
Emitted by ScenarioOrchestrator when an individual scenario's simulation begins. Under ksl.app.config.ExecutionMode.SEQUENTIAL scenarios start one at a time; under ksl.app.config.ExecutionMode.CONCURRENT every scenario emits this event before any of them begin replications.