Computes the weighted sum of player performance Gaussians into a
team-performance variable. Runs once per game (no iteration needed).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Adds the trait that all factors implement and the enum dispatcher
used by the schedule to drive heterogeneous factors without dynamic
dispatch in the hot loop.
The three built-in factors (TeamSum, RankDiff, Trunc) are stubbed
out; concrete implementations follow in tasks 4-6.
