agent-client-protocol-v3.2.0

Added

• (acp) Add retained outgoing request cancellation handles (#409)

Added

• Add RequestCancellationHandle and cancellation_handle() on prepared and
  sent requests. Retain explicit cancellation control while an ordered callback
  or future consumes the response, sharing SDK publication/settlement state and
  once-only cancellation. Handle drop is inert; detaching a request suppresses
  automatic cancellation without revoking retained explicit control.