fix(core): uncap saturate chroma and resolve planeHue as an OKLCH hue

[pbroom]

saturate/desaturate clamped chroma to [0, 0.4], so wide-gamut colors
above 0.4 lost chroma (saturate lowered it, desaturate(c, 0) changed
it). Chroma is now only clamped below at 0, like lighten/darken clamp
lightness to its domain; 0.4 stays as the saturate step span.

planeHue returned the model's own hue on HSL, HSV and HCT planes, but
its callers (gamut boundary, contrast and chroma-band queries and their
result hue) expect an OKLCH hue. It now converts the fixed color, and
falls back to the model hue's most saturated color when that fixed color
is achromatic.

Found while documenting the public API in #235. Each finding was reproduced against the built package before the fix, has a regression test, and its affected JSDoc examples were recomputed. lint, build, test, format:check, typecheck, size, check:artifacts, check:preprod and agents:check:strict pass.

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-08T03:29:51.040535Z	51241a5	PR opened

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[greptile-apps]

Confidence Score: 5/5

[Medium risk] Adjusts color saturation and hue resolution logic.

This PR appears safe to merge; no actionable issue was found.

What we checked:

• Unknown models cannot select functions: planeHue checks the model before reading SATURATED_HUE_SAMPLES. Only supported model names pass, and the samples are fixed functions.

Summary

Removes the upper chroma cap from saturate and desaturate, while keeping the lower bound at zero.

• planeHue now converts HSL, HSV, and HCT colors to an OKLCH hue.
• Achromatic colors use a saturated sample of their model hue.
• Adds regression tests, updates query documentation, and includes a patch changeset.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A["planeHue"] --> B{"Finite explicit hue?"}
  B -- Yes --> C["Normalize and return"]
  B -- No --> D{"OKLCH plane with fixed hue?"}
  D -- Yes --> C
  D -- No --> E["Convert fixed color to OKLCH"]
  E --> F{"Achromatic HSL, HSV, or HCT color?"}
  F -- Yes --> G["Convert saturated hue sample"]
  F -- No --> H["Return converted hue"]
  G --> H

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_{Reviews (1) · Last reviewed commit: "fix(core): uncap saturate chroma and res..." · Reviewed by Greptile}

[pbroom]

Reviewed the full incremental PR and its corrections at d8af837fc1ac1a1cee4d32e4d1551288abbafcd1. Saturate and plane hue reviewed; inherited gradient tests preserved. No remaining actionable findings in the reviewed scope.

Independent correction re-reviews and stack preservation verification passed. At the integrated tip, lint, full build/DTS, 2,208 tests, formatting, strict agent checks and 14 built-site Chrome tests passed. All recorded actionable review threads are addressed. Hosted CI is being verified separately; this review does not authorize merge or release.

[pbroom]

Merge activity

• Oct 10, 6:47 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Oct 10, 8:10 PM UTC: Graphite rebased this pull request as part of a merge.
• Oct 10, 8:11 PM UTC: @pbroom merged this pull request with Graphite.