Issue #129: an all-DNC race must not count toward the discard threshold.
5 scheduled races, but race 3 is all-DNC. The discard threshold says "1 discard at 5 races sailed". Because only 4 races were actually sailed, the threshold does not fire — no discards.
Without the fix this fixture would have triggered a discard (race count = 5 ≥ threshold) and every boat would have discarded the all-DNC penalty (6 pts), which is exactly the bug the issue calls out.
Also covers the edge case from issue #129 open questions: race 5 has a single finisher and the rest DNC — this is *not* an empty race, it scores normally (the single finisher gets 1 pt, others get 6 pts DNC).
Scoring configuration: 1 discard from race 5. DNF/OCS scoring: A5.2 (series entries).
Race 3: abandoned, all DNC → excluded from scoring.
Race 5: only Alice finishes — this *is* a valid race (one finisher),
so it scores normally. Bob and Carol get DNC = N+1 = 4 pts each.
4 sailed races (race 3 excluded). Threshold "5 races → 1 discard" doesn't
fire because sailedRaceCount = 4. No discards. Excluded race contributes 0.