The person-count heuristic was causing widespread flickering (#237, #249,
#280, #292) because:
1. Threshold 0.50 for 2-persons was too low — multipath reflections in
small rooms easily exceeded it
2. No actual hysteresis despite the comment claiming asymmetric thresholds
3. EMA smoothing (α=0.15) was too responsive to transient spikes
Changes:
- Raise up-thresholds: 1→2 persons at 0.65 (was 0.50), 2→3 at 0.85 (was 0.80)
- Add true hysteresis with asymmetric down-thresholds: 2→1 at 0.45, 3→2 at 0.70
- Track prev_person_count in SensingState for state-aware transitions
- Increase EMA smoothing to α=0.10 (~2s time constant at 20 Hz)
- Update all 4 call sites (ESP32, Windows WiFi, multi-BSSID, simulated)
Fixes#292, #280, #237
Co-authored-by: Reuven <cohen@ruv-mac-mini.local>
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