Logged sensor-issue date ranges (auto-detected + manual). Ranges here are
excluded from the PR calculation (contract: test period extends during sensor
unavailability) unless marked ignored. Types: gap
= sensor absent (removal/calibration/comms) · zeros
= flat zero while sibling sensors see sun (dead channel / outage era) ·
flatline = stuck non-zero value ·
manual = user-entered.
Add comments (e.g. “removed for recalibration”, “failed, replaced 2026-01-05”) — they’re preserved across rescans.