Visibility

Rayleigh scattering coefficient and maximum visual range for a clean Rayleigh atmosphere. The scattering coefficient b_sg scales as λ^-4 (Seinfeld & Pandis 2006, Chapter 15, Problem 15.1A), and the maximum visual range x_v_max = 3.912/b_sg (Eq. 15.36). Both outputs depend only on temperature, pressure, and wavelength — no aerosol loading. Migrated from Aerosol.jl src/mie_scattering.jl `RayleighAtmosphere`.

Visibility calculation from extinction coefficient. Computes visual range using the Koschmeider equation (Eq. 15.36) and related visibility metrics. Visual range is the distance at which a black object against a white background reaches the threshold contrast of 0.02.