Class IdlePollingTransfer<T>

Reactive channel with fallback polling on idle incoming data.

Capabilities: isInput, isOutput, isDuplex, isPushable, isPullable, isSubscribable, isPollingSource, isTriggerable, isGate

Mechanics:

1. push(data) — writes the value, notifies subscribers, clears _state, resets the idle timer and stops polling if it was active
2. If no data arrived via push() for longer than timeout ms — an internal Ticker (via tickerFactory) starts, periodically polling the fetcher at interval
3. trigger() — manually calls the fetcher and notifies subscribers, restarts the idle timer
4. pull() — calls the fetcher directly (without writing to state or notifying subscribers)
5. subscribe(handler) — subscribes to notifications
6. activate()/deactivate()/toggle() — control idle monitoring
7. destroy() — stops timers, unsubscribes subscribers, clears state

Error handling:

• If fetcher() throws an exception in trigger() or during polling, onError is called.
• With onError provided, the exception is suppressed (polling continues).
• Without onError, the exception is rethrown.

Configuration (IdlePollingTransferConfig):

• fetcher: DataFetcher — 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 — initial value in _state
• tickerFactory?: TickerFactory — custom ticker factory (default: RAFTicker.factory)
• onError?: ErrorHandler — fetcher error handler

Use cases:

• Refreshing data from an API when the external source stops sending events
• Heartbeat / keep-alive mechanism: polling on absence of incoming data
• Fallback data source when the main stream is idle