Class PollingFlowTransfer<T>

Output transfer with polling from OutputFlowInterface (e.g., Storage).

Capabilities: isOutput, isPollingSource, isPullable, isSubscribable, isTriggerable, isGate

Mechanics:

1. The constructor accepts config.flow: OutputFlowInterface and config.interval
2. An internal Ticker (RAFTicker by default) calls trigger() at the specified interval
3. trigger() — calls flow.read(), writes the result, notifies subscribers
4. pull() — calls flow.read() directly (without writing to state)
5. subscribe(handler) — subscribes to periodic updates
6. activate()/deactivate()/toggle() — control polling
7. destroy() — stops the ticker, unsubscribes subscribers

Error handling:

• If flow.read() throws an exception in trigger() or pull(), onError is called.
• With onError provided, the exception is suppressed.

Configuration (PollingFlowTransferConfig):

• flow: OutputFlowInterface — data source with a read() method
• interval: number — polling interval (ms)
• activated: boolean — initial polling state
• tickerFactory?: TickerFactory — custom ticker factory (default: RAFTicker.factory)
• onError?: ErrorHandler — error handler

Difference from PollingSourceTransfer:

• Uses FlowInterface instead of DataFetcher
• Convenient for working with Storage (LatestStorage, QueueStorage, StackStorage)

Use cases:

• Periodic reading from storage
• Polling state from shared storage
• Integration with external sources via FlowInterface