clayInnerShade function
The inner bottom-right shade of face: L − depthPermille / 1000,
chroma × 1.12 (gamut-mapped), opaque.
Implementation
int clayInnerShade(int face, int depthPermille) {
final f = argbToOklch(face | 0xFF000000);
final l = _max(0, f.l - depthPermille / 1000);
return oklchToArgb(l, f.c * 1.12, f.h);
}