Fix RGB channels drifting when only alpha is changed

[omgovich]

Fixes #163. Alternative to #184.

Why

Moving only the alpha slider changed the RGB channels too: { r: 200, g: 120, b: 35, a: 0.5 } became { r: 199, g: 119, b: 34 } after an alpha-only interaction. The root cause is that rgbaToHsva rounds h/s/v to integers, so the internal HSVA representation loses precision and fromHsva(toHsva(color)) doesn't round-trip.

What changed

• rgbaToHsva no longer rounds its result — the internal HSVA state keeps full precision. All output conversions (hsvaToRgba, hsvaToHex, etc.) still round, so the values emitted by onChange are unchanged in format.
• This fixes the drift for RgbaColorPicker, RgbaStringColorPicker and HexAlphaColorPicker in one place, with no new API and no size cost (unlike Fix RGBA calc error when change alpha #184, which added an updateAlpha method to every color model and went over the size limit).
• Added regression tests: an alpha-only interaction must keep the RGB channels (RgbaColorPicker) and the hex color (HexAlphaColorPicker) intact.
• Updated four existing tests in tests/utils.test.js that asserted rounded values from input converters — they now compare via roundHsva, same semantics.

Verified exhaustively outside the test suite: with rounding removed, hsvaToRgba(rgbaToHsva(c)) round-trips exactly for all 16.7M RGB values.

How to review

The production change is only rgbaToHsva in src/utils/convert.ts — three round() calls removed. Worth double-checking that nothing user-visible relies on the internal HSVA being integers: the UI components already round for aria-* output, and hslaToHsva never rounded to begin with. Bundle size is neutral (±1 B gzip noise).

[github-actions]

Size Change: -2 B (-0.04%)

Total Size: 4.91 kB

📦 View Changed

Filename	Size	Change
dist/index.module.js	4.91 kB	-2 B (-0.04%)

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