Per-race options — 'must count' and a DNE are different protections, and both apply at once

RRS A5 / A9: a DNE (disqualification not excludable) cannot be discarded whatever race it was scored in. That is a property of the *code*. "Must count" is a property of the *race*, set from the NoR. A boat can meet both in one series, and each removes a different column from its discard pool.

Scoring configuration: 1 discard from race 4. DNF/OCS scoring: A5.2 (series entries).

Alice is disqualified without the right to exclude the score (DNE = N+1 = 5).
Points, then what each boat may discard:
  Alice: 1, 3, 5(DNE), 1 — total=10. Race 2 must count, race 3 is a DNE →
         only races 1 and 4 available, both 1s → drop race 1. net=9.
  Bob:   2, 1, 1, 2 — total=6.  Races 1, 3, 4 available → drop race 1 (2). net=4.
  Carol: 3, 2, 2, 3 — total=10. Races 1, 3, 4 available → drop race 1 (3). net=7.
  David: 4, 4, 3, 4 — total=15. Races 1, 3, 4 available → drop race 1 (4). net=11.