Mcarthur

Coupled atmosphere-fire model for a dry eucalyptus forest implementing the McArthur fire-spread formula and four-fuel-type consumption from Clark et al. (1996). Migrated from WildlandFire.jl@126976f2 src/clark1996.jl:81 (`Clark1996FireSpread` @component). Five ODE states (M_litter, M_trash, M_scrub, M_canopy, Q_cumulative) and seven algebraic state variables (B_ratio, S_f, canopy_burning, ground_burn_rate, total_burn_rate, F_s, F_l). The cumulative ground heat flux Q_cumulative drives an automatic canopy ignition threshold at 170 kJ/m^2 (p. 180, Clark et al. 1996); each ground fuel is gated by an ifelse against eps_fuel so consumption stops cleanly when the pool is depleted.