- SharedPacketHandler.handle_packet_update: dispatch on filter-result,
and use maybe_enrich/2 dispatched on the enrich? boolean instead of
an inner `if`. lookup_device_info/1 is now a trio of function heads.
- Cluster.Topology.child_spec: build_spec/3 dispatches on
(cluster_enabled?, topologies) tuples — no more nested `if`.
- Cluster.PacketDistributor.distribute_packet: maybe_broadcast/2
dispatches on the leader-and-enabled check; the non-leader / disabled
paths return :ok explicitly instead of relying on an `if` expression's
implicit nil.
Adds tests for SharedPacketHandler (filter/enrich/match paths,
callsign_filter + callsign_and_weather_filter factories) and extends
Cluster.Topology tests to cover the nil-topology and opts-merge cases.
Coverage 66.41 → 66.81%.
