Invoice a nursery's families for a month with weekly funded hours, a term-start age rule and a sibling discount

# Invoice a nursery's families for October 2026 Inputs: `children.csv` (child id, family id, date of birth), `attendance.csv` (hours each child attended each day in October 2026) and `fees.json`. Invoice rules: - Funded hours: a child who was 3 or older on 2026-09-01 gets up to `funded_hours_per_week` hours free in each Monday-to-Sunday week (the part-week 1-4 October counts as a week); unused funded hours don't carry to another week. - Charged hours = attended hours minus funded hours used; hours fee = charged hours x `hourly_rate`. - Sibling discount: `sibling_discount_pct` off the hours fee (not meals) of every child in a family except the oldest child who attended in October. - Meals: `meal_per_day` for each day attended. - Each child's total = hours fee after discount + meals, rounded half-up to the cent. A family's total is the sum of its children's rounded totals. Write `out/invoices.json`: `{"funded_hours_used": {"<child_id>": <hours>, ...}, "child_totals": {"<child_id>": <total>, ...}, "family_totals": {"<family_id>": <total>, ...}}` for every child and family that attended in October. ## How this run works - Work on your own: nobody will answer questions in this task, and writing to `ask/` counts against the run. - Write only under `out/`. Create `out/` if it is missing. Inputs are synthetic; don't fetch anything from the network. - Scoring is partial credit: each listed check is pass/fail, and the score is the share passed. Numbers are compared to within 0.005 unless the task says otherwise.