- Extract PathParser.valid_callsign?/1 and reuse from the calibration
Mix task instead of duplicating the regex.
- Document raise behavior on Aprs.recent_packets_with_paths/1 and
Aprs.station_positions/1 (already noted in moduledoc; @doc reinforces
for callers reading the function head).
- Note in the BandConfig guard comment why it sits before the Oban pause
(so a misconfig exits without leaving queues paused).
- Reword the band-mismatched-negatives note as a v1 limitation (no TODO
tag — codebase convention is zero TODOs).