The engine now passes each reception's radio to the neighbour link
tracker, from both the forwarding path and the duplicate-recording path,
so /neighbor_links can report how each radio hears a neighbour.
Two radios sharing one frequency hear each other transmit. The echo of a
relayed flood ends in this node's own path hash, so the tracker recorded
the node as its own neighbour, at near-zero-dB signal. The engine now
remembers the packet hash and exact path of each transmission for 30 s,
registered before the first send because an echo can arrive while a
later egress of the same fan-out is still on the air, and skips tracker
observation for a reception that matches. A neighbour repeating our copy
appends its own hash and still counts. The echo is still stored and
published as the reception it is; only the neighbour table ignores it.
Matching the exact path rather than the last hop's hash keeps a real
neighbour whose 1-byte hash collides with ours.