createHTLC

async createHTLC({
  receiverSparkAddress,
  amountSats,
  preimage,
  expiryTime,
}: {
  receiverSparkAddress: string;
  amountSats: number;
  preimage?: string;  // Optional - auto-generated if not provided
  expiryTime: Date;
}): Promise<Transfer>

// With auto-generated preimage (recommended)
const htlc = await wallet.createHTLC({
  receiverSparkAddress: "spark1...",
  amountSats: 10000,
  expiryTime: new Date(Date.now() + 3600000) // 1 hour from now
});
console.log("HTLC created:", htlc.id);

// With custom preimage
const htlcWithPreimage = await wallet.createHTLC({
  receiverSparkAddress: "spark1...",
  amountSats: 10000,
  preimage: "abc123def456...", // 32 bytes hex
  expiryTime: new Date(Date.now() + 3600000)
});