Oklab: Fix rollover error

[xkns]

Summary
The Oklab reference implementation (#1477) can under some circumstances output RGB colors (components of type double) with slightly negative values. (I'm not sure if this is due to imprecise operations or just the nature of the internal gamut mapping.)

When converting those double components back to bytes a rollover could occur leaving the affected component with a value of 255 instead of the intended 0.

This PR fixes that issue by clamping the components just before type conversion happens.

And sorry for not catching this with the initial PR.

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of web configuration, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing setups:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's body (e.g. Fixes: #xxx[,#xxx], where "xxx" is the issue number)

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated (docs/docs/en)
• Related tests have been updated

PLEASE DON'T FORGET TO ADD YOUR CHANGES TO CHANGELOG.MD

• Yes, CHANGELOG.md is also updated
• Kinda, CHANGELOG.md has an entry, for the feature this is fixing (Saturation & Brightness/Value Gain using Oklab color space #1477), still pending

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[hyperion-project]

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