Elliptical_fire

Fire spread from a single ignition point assuming an elliptical fire shape — calculates eccentricity, spread rate in arbitrary direction, backing fire spread, fire length and width, flanking distance, and ellipse geometric parameters (semi-major axis, focus offset, semi-minor axis). Migrated from WildlandFire.jl@126976f2508ceacca6c486b21ae6da5b168c6f46:src/fire_spread_direction.jl:174 (`EllipticalFireSpread` @component). Algebraic-only: R_H, Z, γ, elapsed_time are inputs (parameters); e, R_γ, R_B, D_H, D_B, L, W, D_F, f, g, h are algebraic outputs.