feat(theme-studio): add color-family sort

sortFamilies orders the strips for display: neutrals first by lightness, then chromatic families by base hue, ties broken by base lightness then base hex. Each family's members come back sorted dark to light. Hue is compared rounded so a sub-degree hue hair from gamut quantization doesn't outrank lightness. Sorting is display-only; the stored palette order is untouched.

Phase 2 of the color-families spec, pure logic. Four node tests cover the hue order, the neutral pin, within-family lightness order, and the (hue, then lightness) ordering invariant. Suite 91 to 95 green.

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