PR #53 (7ff3010c) collapsed iter_downlink_voice_slots to one delivery
slot for any peer, but peer_listen_slots only ever returns more than one
slot for a peer already confirmed duplex via peer_is_simplex -- so that
collapse could only suppress real duplex hotspots, not the unpaced
software bridges (ysf2dmr/adn-bridge) it was meant to fix, since those
already collapse correctly via their own simplex classification.
Trust peer_listen_slots directly again. Confirmed live: a duplex hotspot
with a TG on both static OPTIONS slots now receives it on both timeslots
regardless of which slot the source transmitted on.
Introduce downlink.py as the single authority for hotspot eligibility (OPTIONS,
slot busy, post-TX GROUP_HANGTIME). send_peer and BRDG fan-out share the same
gate; monitor events carry stream id from BRDG so new QSOs after hangtime
display without replaying calls blocked during the hangtime window.
Planned release: 2.2.0