docs/img/backtest-2024-p1.png: observed P.1 level vs the 24h-ahead
predicted peak issued at each hour by a model trained only on pre-flood
data, with the warning-probability panel below (first alert 24 Sep
01:00, 24 h before flooding began). Embedded in FLOOD_FORECASTING.md's
headline-validation section with an honest reading, including the
~0.4 m peak under-prediction.
Replay pacing is now adaptive: 4 h/frame through quiet days, 2 h when
risk is elevated, 1 h (hour-by-hour) while the model is alerting or the
river is near/above flood stage - so viewers can watch the detection
sequence unfold.
