Fuel_consumption

Fuel consumption model: exponential decay of remaining fuel fraction F after ignition, per Eq. 3 of Mandel et al. (2011). Migrated from WildlandFire.jl src/level_set_fire_spread.jl:243 (`FuelConsumption` @component). The fuel-fraction ODE D(F) = -is_burning*F/T_f decays with time constant T_f when is_burning ≈ 1; the algebraic w0_effective = F*w0_initial feeds the FireHeatFlux component in the coupled WRF-SFIRE pipeline.