Surface native (Galaxy/MxGateway) alarms by their object-relative reference
(e.g. "Z28061.HeartbeatTimeoutAlarm") instead of the gateway's full provider
reference ("Galaxy!<area>.<object>.<alarm>"). The area is already preserved in
Category and the object reference is globally unique within the galaxy, so the
full provider prefix added only noise to the alarm identity operators see.
MxGatewayAlarmMapper.MapTransition/MapSnapshot now set SourceReference from
SourceObjectReference, falling back to AlarmFullReference only when the gateway
omits the object reference. +2 mapper tests; full DCL suite green (158).
Joseph Doherty