Function apply_confidence_boost 

pub fn apply_confidence_boost(distance: f32, confidence: u8) -> f32

Apply an evidence-confidence boost to the rank distance.

confidence is 0..100 (0 = no evidence). The boost is subtracted from the divisor, so higher confidence means lower distance (better rank). A confidence of 50 reduces the distance by ~5%; 100 by ~10%.

The boost is gentle — it cannot dominate lexical or spatial distance, it only orders memories with the same content by how much evidence stands behind them. C1: recall frequency never affects this.