Compute final course grades with late penalties, a dropped homework and excused items

# Compute final course grades from a gradebook Inputs: `syllabus.json` (category weights, letter cut-offs, late rule) and `gradebook.json` (each student's scores per assignment: points earned, points possible, days late, or "EX" for excused). Rules: - Excused ("EX") items are left out of both earned and possible points. - Late homework loses 10% of its earned points per day late, up to 3 days (so at most 30%). Only homework has a late penalty. - Drop each student's single lowest homework, by percentage of possible points after the late penalty (on a tie, drop the earlier one). Excused items can't be dropped. - Category percentage = sum of earned points / sum of possible points x 100, using the remaining items. - Final percentage = sum of category percentage x category weight, rounded half-up to 2 decimal places. - Letter grade comes from the rounded final percentage and the cut-offs in syllabus.json (a cut-off is a minimum, inclusive). Write `out/grades.json`: `{"<student_id>": {"homework_pct": <number>, "quiz_pct": <number>, "exam_pct": <number>, "final_pct": <number>, "letter": "<A-F>"}, ...}`. Category percentages are checked to within 0.01. ## 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.