Replace the blind transferComplete.await() with a polling-based stall detector that checks buffer growth every 3 seconds. If data stops arriving for 6 consecutive seconds (2 polls), the transfer is considered stalled and automatically retried.

This catches a real-world failure mode where the BLE connection stays alive but the firmware stops sending notifications (e.g. Android drops some packets silently). The previous approach would wait the full timeout (45s) before retrying, while this detects the problem in 6 seconds.

Also splits the broad catch(Exception) into specific handlers for TimeoutCancellationException, IOException, and CancellationException for clearer error logging.