gt06_calibration.json:
offset = voltage-divider bias (reads high +), R = internal resistance
(both solid). Capacity/Wh are nominal-anchored estimates from a shallow
discharge (relative ordering meaningful, absolute soft pending a deep discharge).
Max time = Wh / per-mode power: track ~0.43 W, idle ~0.28 W
(* preliminary — idle keeps the LTE link up so it's
most of tracking; GPS-off saves little), sleep pending a clean off-charge MODE5 night.
Grey rows = defaults (unseen unit); orange = uncertain fit.