The receiver already sends a PASSKEY_PRESSED notification for every accepted
key or button press during pairing, but the handler discarded all of them.
Count them instead: address 0x00 marks the start of entry, 0x01 one accepted
press, and 0x04 the terminator. Any other address is left alone, since the
rest of that address space is undocumented and a miscounted press is worse
than no count at all.
The notification carries no indication of which button was pressed, so only
the number of accepted presses can be derived from it.
Deliberately does not call receiver.changed(): that path drives the tray, the
main window and desktop notifications, and would fire once per press.
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