Function flip_threshold

pub fn flip_threshold(
    config: &GameConfig,
    collection: &ArtifactCollection,
) -> f64

The flip threshold this collection actually plays against.

ART-03 Halfway Bell is the only artifact that moves it, and it moves it as a share of whatever FlipSettings::progress_threshold is configured — so a later rebalance of the threshold keeps meaning “at 60% of the bar”. Every other collection (and every player with nothing worn) gets the configured threshold unchanged.

This is the single reader of the law: gauge accumulation, the VA-01 ramp, the HA-04 half-gauge gate and the equip-time re-denomination all call it, so there is exactly one definition of “the bar” per character.