Function effective_sg_from_inputs 

pub fn effective_sg_from_inputs(
    inputs: &BallisticInputs,
    temp_c: f64,
    press_hpa: f64,
) -> f64

Canonical muzzle gyroscopic stability Sg for the empirical Litz spin-drift model, shared by cli_api and the fast / Monte-Carlo path so every solver family uses ONE Sg (MBA-1134, rank 31).

Delegates to crate::stability::compute_stability_coefficient, the single source of truth for Miller Sg. That INCLUDES the (v/2800)^(1/3) muzzle-velocity term (matching the reported SG and the aerodynamic-jump Sg) and the linear Miller density correction (T/T0)*(P0/P). temp_c / press_hpa are the resolved muzzle atmosphere.

compute_stability_coefficient returns 0.0 when bullet_length is unset, so this first substitutes a length estimate. MBA-1135: use the mass-based crate::stability::estimate_bullet_length_m (falling back to the historical 4.5-caliber literal only when mass is unavailable) instead of a mass-blind 4.5-caliber default, so heavier/longer bullets get a physically consistent Sg.