fix: deliver one DMRD when TG is on both OPTIONS slots (#53)

Dual-slot fan-out from TS1+TS2 static OPTIONS doubled OBP/HBP
downlink rate and made unpaced bridges (e.g. ysf2dmr) sound slow.

src/adn_server/application/routing/downlink.py

@@ -91,7 +91,12 @@ def normalize_ua_voice_slot(peer: dict[str, Any], wire_slot: int) -> int:
 
 
 def peer_listen_slots(peer: dict[str, Any], tgid: int) -> list[int]:
-    """Voice slots where this peer listens for ``tgid`` (static OPTIONS or wire fallback)."""
+    """Candidate RF slots where this peer is subscribed to ``tgid`` (OPTIONS).
+
+    When the same TG is listed on both TS1 and TS2, both slots are returned as
+    candidates; :func:`iter_downlink_voice_slots` collapses that to **one**
+    delivery slot (never duplicate DMRD).
+    """
     from adn_server.application.report.payloads import parse_peer_options_static
 
     ts1, ts2 = parse_peer_options_static(peer.get("OPTIONS"))
@@ -651,10 +656,20 @@ def iter_downlink_voice_slots(
     wire_slot: int,
     tgid: int,
 ) -> list[int]:
-    """P4: slots to deliver when static TG spans TS1+TS2."""
+    """Exactly one voice slot for group downlink to this peer.
+
+    Legacy ``send_peers`` sends one DMRD per peer. If OPTIONS lists the same TG
+    on TS1 and TS2, keep a single copy on the bridge/OBP wire slot (remap only
+    when the peer listens on a different unambiguous slot).
+    """
     listen = peer_listen_slots(peer, tgid)
+    if len(listen) > 1:
+        ws = int(wire_slot)
+        if ws in listen:
+            return [ws]
+        return [int(peer_downlink_voice_slot(peer, wire_slot, tgid))]
     if listen:
         return listen
     if peer_receives_group_tgid(peer, wire_slot, tgid):
         return [peer_downlink_voice_slot(peer, wire_slot, tgid)]
-    return [wire_slot]
+    return [int(wire_slot)]

tests/application/test_downlink_stabilization.py

@@ -25,6 +25,7 @@ from __future__ import annotations
 from adn_server.application.routing.downlink import (
     DownlinkContext,
     iter_downlink_voice_slots,
+    peer_listen_slots,
     peer_slot_blocks_downlink,
     synthetic_group_dmrd_route_packet,
     touch_peer_voice_slot,
@@ -169,10 +170,20 @@ def test_inject_only_hangtime_blocks_static_tg_after_dynamic_tx() -> None:
     assert not peer_slot_blocks_downlink(ctx, peer_id, peer, same7306, pkt_time=now + 8)
 
 
-def test_same_static_tg_on_both_slots_delivers_twice() -> None:
-    """P4: TG listed in TS1 and TS2 OPTIONS maps to both voice slots."""
+def test_same_static_tg_on_both_slots_delivers_once_on_wire_slot() -> None:
+    """TG on TS1+TS2 OPTIONS: one DMRD on the bridge wire slot (not dual fan-out)."""
     peer = {"OPTIONS": b"TS1=730444;TS2=730444;"}
-    assert iter_downlink_voice_slots(peer, 1, 730444) == [1, 2]
+    assert iter_downlink_voice_slots(peer, 1, 730444) == [1]
+    assert iter_downlink_voice_slots(peer, 2, 730444) == [2]
+    # Subscription still visible on both; delivery collapses in iter_*.
+    assert peer_listen_slots(peer, 730444) == [1, 2]
+
+
+def test_static_tg_on_one_slot_unchanged() -> None:
+    peer_ts2 = {"OPTIONS": b"TS2=9140;"}
+    assert iter_downlink_voice_slots(peer_ts2, 1, 9140) == [2]
+    peer_ts1 = {"OPTIONS": b"TS1=9140;"}
+    assert iter_downlink_voice_slots(peer_ts1, 2, 9140) == [1]
 
 
 def test_hp3icc_style_slot_busy_until_vterm() -> None: