DupePacketFilter.filter() was checking packet.processed (the newly
arrived duplicate) instead of found.processed (the previously stored
packet). Since all freshly decoded packets have processed=False by
default, the dupe detection branch was never reachable — every
duplicate message was passed through and re-processed.
This caused KM6LYW's retransmit of msg:9028 (via a different
digipeater path 63s after first receipt) to trigger NearestPlugin
a second time, sending 4 reply packets instead of 2 and resetting
the AckPacket retry counter back to (1 of 3).
Fix: check found.processed instead of packet.processed.
Update existing tests to reflect the correct variable under test.
Add regression test test_filter_aprs_retransmit_via_different_digi
that reproduces the exact production scenario.
hemna