Signal closed notification. Emitted when a trading position is closed (TP/SL hit).
type: "signal.closed"
id: string
timestamp: number
backtest: boolean
symbol: string
strategyName: string
exchangeName: string
signalId: string
position: "long" | "short"
priceOpen: number
priceClose: number
pnlPercentage: number
closeReason: string
duration: number
note: string