fix(router): never forward control packets to the engine

MeshCore never relays control packets: the direct high-bit discovery
subset is explicitly released and any other control payload hits the
switch default that does not flood-route unknown types. Mark control
packets do-not-retransmit unconditionally instead of only when discovery
is enabled, so a repeater with discovery disabled no longer forwards
control/discovery traffic.

repeater/packet_router.py

@@ -475,10 +475,17 @@ class PacketRouter:
                 # as routing hashes and log bogus duplicate rows.
 
         elif payload_type == ControlHandler.payload_type():
+            # MeshCore never relays control packets: the direct high-bit discovery
+            # subset is explicitly released (Mesh.cpp), and any other control
+            # payload hits the switch default that does not flood-route unknown
+            # types. Mark do-not-retransmit unconditionally so a repeater with
+            # discovery disabled still does not forward control/discovery traffic
+            # to the engine. Discovery responses are injected as their own TX, so
+            # this does not suppress them.
+            packet.mark_do_not_retransmit()
             # Process control/discovery packet
             if self.daemon.discovery_helper:
                 await self.daemon.discovery_helper.control_handler(packet)
-                packet.mark_do_not_retransmit()
             # Deliver to companions via daemon (frame servers push PUSH_CODE_CONTROL_DATA 0x8E)
             deliver = getattr(self.daemon, "deliver_control_data", None)
             if deliver:

tests/test_packet_router.py

@@ -546,6 +546,19 @@ class TestPacketRouterRoutingBranches(unittest.IsolatedAsyncioTestCase):
         daemon.deliver_control_data.assert_awaited_once()
         daemon.repeater_handler.assert_awaited_once()
 
+    async def test_route_control_marks_do_not_retransmit_when_discovery_disabled(self):
+        """With discovery disabled (discovery_helper is None), control packets must
+        still be marked do-not-retransmit so the engine does not relay them. MeshCore
+        never forwards control packets regardless of whether discovery is enabled."""
+        daemon = _make_daemon()
+        daemon.discovery_helper = None
+        daemon.deliver_control_data = AsyncMock()
+        router = PacketRouter(daemon)
+        pkt = _make_packet(ControlHandler.payload_type())
+        pkt.path_len = 0
+        await router._route_packet(pkt)
+        pkt.mark_do_not_retransmit.assert_called_once()
+
     async def test_route_advert_delivers_to_helpers_and_engine(self):
         daemon = _make_daemon()
         daemon.advert_helper = MagicMock()