Only TrailBook was covered; the HA-facing half — subscription callback,
attribute dialects, map-id resolution, run end on docking — had no test
at all. It does now, against a stubbed hass, which is also where the
missing behaviour showed up: recording started at the NEXT state change,
so an HA restart (or finishing calibration) mid-cleanup dropped the
opening seconds of the path. Sampling is factored out and runs once per
source on setup and on every refresh.
