ToolBatchEvent
data class ToolBatchEvent(val timestamp: Instant = Clock.System.now(), val correlationId: String, val batchId: String, val toolNames: List<String>, val successCount: Int, val failureCount: Int, val callDuration: Duration, val caller: String? = null) : TracerEvent
Records the end-to-end execution of a parallel tool batch.
Per-call detail still lands as ToolCallEvent events; the batch event lets observers measure parallelism gains and correlate calls dispatched together. Parity with the Rust and TypeScript ports.