Class ChannelTransfer<T>

Output channel with external management via setup/destroy callbacks.

Capabilities: isOutput, isSubscribable

Mechanics:

1. The constructor accepts config with callbacks:
   • setup(emit) — called immediately, receives the emit(data) function
   • destroy() — cleanup function (called on transfer destroy)
2. setup() should call emit(data) to send data to subscribers
3. subscribe(handler) — subscribes to notifications
4. destroy() — calls config.destroy(), unsubscribes subscribers

Error handling:

• onError — for errors in emit() (when sending data to subscribers)
• onDestroyError — for errors in destroy()
• With the corresponding handler provided, the exception is suppressed.
• Without a handler, the exception is rethrown.
• setup() errors are always rethrown (no onSetupError — a failed setup means the transfer is unusable, suppressing would create a zombie object).

Configuration (ChannelTransferConfig):

• setup: (emit: DataHandler) => void — channel initialization
• destroy: () => void — channel cleanup
• onError?: ErrorHandler — emit() error handler
• onDestroyError?: ErrorHandler — destroy() error handler

Difference from StoredChannelTransfer:

• No pull() — only reactive subscription
• No trigger() — emission only via external emit()
• _state does not store a value for reading (cleared after sendState)

Use cases:

• Integration with external event sources (WebSocket, DOM events)
• Adapting legacy API to pipeline
• Custom data sources with their own logic