Outcome::winner(i, n), Outcome::draw(n), Outcome::ranking(iter) are
the convenience constructors. Marked #[non_exhaustive] so Scored can
be added in T4 without breaking match exhaustiveness.
Adds smallvec = "1" as a direct dependency.
Part of T2 of docs/superpowers/specs/2026-04-23-trueskill-engine-redesign-design.md.