Constant RECENCY_WEIGHT 

pub const RECENCY_WEIGHT: f64 = _; // 0.0083333333333333332f64

G12-recency — additive recency weight, smaller than one RRF rank-step (1/(RRF_K+1) ≈ 0.0164) so recency breaks near-ties and nudges but never overrides a clear RRF signal. Conservative by construction.