Function interpolated_bc 

pub fn interpolated_bc(
    mach: f64,
    segments: &[(f64, f64)],
    inputs: Option<&BallisticInputs>,
) -> f64

Interpolate a ballistic coefficient from Mach-keyed segments.

An empty optional table is not a request to invent a new BC: when inputs are present, the caller’s scalar bc_value is preserved. Standalone calls without inputs retain the historical conservative fallback because no caller BC is available.