feat: add optional AbortSignal to every public async method

[ZacLou]

Summary

Addresses #604

Problem

Some methods threaded { signal }, others didn't. There was no consistent way for callers to cancel an in-flight operation.

Changes

StreamsModule (13 methods)

Added signal?: AbortSignal to: get, withdrawable, streamedTotal, withdraw, cancel, pause, resume, topUp, forceCancel, transferRecipient, clawback, estimateFee, list

FactoryModule (5 methods)

Added signal?: AbortSignal to: streamCount, streamAddress, streamsBySender, streamsByRecipient, protocolFeeBps

Internal helpers

• _resolveAddr, _simulateTx, _invoke, and _sendAndPoll now accept signal
• Abort check added at the start of each public method
• Abort check added inside the _sendAndPoll polling loop so confirmation waits can be cancelled

Usage

const controller = new AbortController();

// Cancel after 10 seconds
setTimeout(() => controller.abort(), 10_000);

try {
  const stream = await sdk.streams.get(1n, controller.signal);
} catch (e) {
  if (e instanceof DOMException && e.name === 'AbortError') {
    console.log('Cancelled');
  }
}

Backward compatibility

signal is optional and defaults to undefined. All existing code continues to work unchanged.

Verification

• Typecheck passes
• All 989 tests pass (78 test files)