Function enuDirectionFromAzimuthAltitude

enuDirectionFromAzimuthAltitude(azimuthRad: number, altitudeRad: number): Vec3
Convert a SunCalc azimuth + altitude into a unit ENU direction vector pointing toward the sun. Pure helper, exported mainly for testing; most callers want computeSunState.
Parameters
- azimuthRad: number
  Azimuth in radians, SunCalc convention: 0 = south, positive toward west (clockwise), +π/2 = west.
- altitudeRad: number
  Altitude above the horizon in radians (+π/2 = zenith, negative below the horizon).
Returns Vec3
A unit Vec3 in tile-local ENU (x = east, y = north, z = up) pointing toward the sun.