Function learn 

pub fn learn(
    records: &[DayRecord],
    start: Load,
    window: u32,
    today: Date,
) -> Learned

The budgets and the gain minimum as of today, replayed day by day over records (oldest first; days before today only), from start, with window days of memory. The rules, in order, on each day with an outcome: a drop when it was bad after a full day; a freeze after a flare; the target from informative good days; a rise after a stable week (docs/capacity.md, “Budgets”).