The current status of a task: state (required) + optional message + timestamp.
Timestamp is ISO 8601. Message (if present) is an A2A Message.
Summary
Types
@type t() :: %A2aEngine.Types.TaskStatus{ message: A2aEngine.Types.Message.t() | nil, state: A2aEngine.LifecycleState.t(), timestamp: String.t() | nil }