Function calculate_gyroscopic_drift 

pub fn calculate_gyroscopic_drift(
    stability_factor: f64,
    _yaw_rad: f64,
    _velocity_mps: f64,
    time_s: f64,
    is_right_twist: bool,
) -> f64

Calculate the cumulative empirical Litz gyroscopic-drift component.

velocity_mps is retained for source compatibility but intentionally does not gate the accumulated displacement. A stateless current-velocity check cannot erase or freeze drift accrued earlier in flight; live solver paths use litz_drift_meters directly.