Builds linear, radial or conic gradients (plus repeating variants) from colour stops with optional positions and hint lines, in the sRGB default or CSS Color 4 interpolation spaces (oklch, oklab, hsl, display-p3) with the longer-hue option. Output is a CSS rule with a solid fallback, a Tailwind arbitrary value and a custom property; the SVG equivalent is generated for linear and radial gradients. The preview renders the exact CSS. Everything runs locally.