Suspect Package Detection

The sensor measures distance (mm) from sensor to fill surface every 30 minutes. Regular trash fills gradually at 0.5-3 cm/hr with surface noise of +/-15-30 mm. A package insertion causes a sudden distance drop (>100-300 mm in one reading), followed by a flat surface plateau (stddev <8 mm) as the rigid object rests without compacting. The algorithm scores 7 signals: spike magnitude, fill rate ratio, surface flatness, plateau detection, volume estimation, temperature (rules out fire), and time-of-day.