sampleInfohashes
suspend fun sampleInfohashes(host: String, port: Int, target: Sha1Hash = generateRandomId(random)): DhtNode.SampleResult?
BEP-51 client: ask host:port for a sample of the info-hashes it tracks. Returns the decoded sample (20-byte info-hashes) plus the closest nodes it pointed us at, or null on timeout/parse failure. This is the querier half; most callers only need it for DHT-wide content indexing.