Class AsyncIdlePollingTransfer<T>

Reactive channel with asynchronous fallback polling on idle.

Capabilities: isInput, isOutput, isDuplex, isPushable, isSubscribable, isPollingSource, isAsyncPullable, isAsyncTriggerable, isGate

Mechanics:

1. push(data) — synchronously writes, notifies, clears, resets the idle timer
2. asyncTrigger() — awaits _doPoll() (fetch + notify), then restarts the idle timer
3. asyncPull() — calls await fetcher() directly (without writing to state)
4. If no data arrived for longer than timeout ms — polling starts via Ticker
5. The ticker calls _doPoll() (fire-and-forget)
6. On push — polling stops, the idle timer resets
7. The _polling flag prevents overlapping

Note: push is synchronous (like in the sync version), but the fetcher is asynchronous. Results arrive via sync subscription. asyncTrigger and asyncPull are async methods.

Error handling:

• If fetcher() throws an exception, onError is called.
• With onError provided, the exception is suppressed. Without onError — rethrown from _doPoll.
• asyncTrigger() awaits _doPoll() — caller can catch rethrown errors via await.
• When the ticker fires _doPoll() without onError, the rejection is unhandled (visible in logs as unhandled promise rejection). To suppress — provide onError.

Configuration (AsyncIdlePollingTransferConfig):

• fetcher: AsyncDataFetcher — async data retrieval function for idle polling
• timeout: number — idle time (ms) before polling starts
• interval: number — fetcher polling interval (ms)
• activated: boolean — initial idle monitoring state
• initialValue?: T
• tickerFactory?: TickerFactory
• onError?: ErrorHandler