HWB (Hue-Whiteness-Blackness) color string validation.
Splits out HWB-specific validation from Pote.Validator.
Not part of the public API — used only by Pote.Validator.
Summary
Functions
Returns error messages for HWB validation errors.
Validates an HWB color code: H,W,B (H: 0-360 degrees, W/B: 0.0-1.0).