Extension: turn the reading-based ‘probe dark’ timer into an actual alert (probe dark > N h) – Runtz Punch probe has been DARK 24h+ on a live D62 flowering plan

WHAT: The reading-based dark timer (built this cycle) shows ‘DARK 24H 47M’ on the Runtz Punch probe – a live flowering plant with no soil data for over a day – but this only renders as a chip; no alert fires. The Alerts catalogue has ‘Root-zone probes’ (a probe the HEAT MAT relies on is missing) but nothing for ‘a plant’s probe has been dark > N h’. WHY: a live plant losing its probe for 24h+ is exactly what an operator should be told about; the timer already computes dark_for_s, so the signal exists. HOW: add a catalogue alert ‘Probe dark’ keyed off binary_sensor.dsc_probe_reading_dark.dark_for_s > threshold (operator-set, default e.g. 2-6h), WARN by default. Closes the loop on the dark-timer feature. Found live 8.2.0.