Adds tests for the PromEx supervision module and custom plugin (both
were 0–25% covered), expands the HealthCheck plug to exercise the
readiness success path through the live ShutdownHandler, adds public-API
roundtrip tests for PacketReplay's via_tuple wrappers, and covers
several private-helper fallback branches in Aprsme.Packet
(ParseError data_extended, MicE map symbol defaults, struct
data_extended, weather binary, has_position via legacy lat/lon, PHG /
altitude error parsing).