OneShotSender<T> class final

Promise-like sender for one-shot channels.

Can send exactly one value, after which the channel becomes unavailable for further sends. Perfect for promise resolution patterns.

Characteristics:

• Single-send: Only one send call succeeds
• Direct delivery: Value delivered to waiting receivers
• Auto-disconnect: Channel disconnects after successful send
• Type-safe: Compile-time guarantees about value delivery

Example:

final (promiseTx, promiseRx) = OneShot.channel<Result>();

// Promise resolution
Future<void> resolvePromise() async {
  final result = await computeExpensiveResult();

  // This succeeds
  final sendResult = await promiseTx.send(result);
  assert(sendResult is SendOk);

  // This fails - already sent
  final secondSend = promiseTx.trySend(anotherResult);
  assert(secondSend is SendErrorDisconnected);
}