Hand-rolled transcendentals (sqrt, cbrt, exp, ln, pow, sin, cos, atan, atan2)
via range reduction + series/Newton, since Nix has no math builtins. Verified
against known values to ~1e-6. Foundation for a pure-Nix material-color-utilities
port (goal: drop the matugen IFD).
Assisted-by: pi (opus-4.8)
