test(color-handle): tests and docs (phases 6-7)

[blunteshwar]

Description

Phases 6 (Testing) and 7 (Documentation) of the sp-color-handle → swc-color-handle migration, stacked on the Phase 2–5 work merged via #6443. No component behavior changes.

Testing (Phase 6)

Unit / behavior (test/color-handle.test.ts, Storybook play tests):

• Role-less, name-less host (no role/aria-label/aria-labelledby/tabindex); color applied to the fill layer; adaptive --_swc-color-handle-border-alpha set.
• Touch pointerdown/pointerup/pointercancel open-close; mouse does not auto-open.
• disabled suppresses the built-in loupe even when open.
• fill=false renders outline-only (via the reflected boolean property).

Contrast helper (computeBorderAlpha/findMinAlpha/contrastRatio):

• Parser yields no NaN across named/hex/rgb/hsl/rgba; floor fallback for invalid input; white-first holds the floor when white carries 3:1 and escalates otherwise. Regression test for the parser concern raised in feat(color-handle): scaffold 2nd-gen core/SWC structure (Phase 2&3) #6443 review.

Accessibility (test/color-handle.a11y.spec.ts, Playwright):

• Role-less/name-less host and built-in loupe SVG aria-hidden across chromium/firefox/webkit.

Documentation (Phase 7)

• New per-component MDX (color-handle.mdx): Anatomy, Options (Colors, Fill), States, Behaviors (Adaptive contrast), Accessibility (features + best practices), and Upcoming features. Documents the handle as a visual primitive whose name/role/value/keyboard belong to the parent color-area/slider/wheel.
• Stories: dropped autodocs from Playground so the MDX is the single docs page (kept dev); finalized the Accessibility story.
• Public prop JSDoc lives on ColorHandleBase and feeds the Storybook <ApiTable />; no public --swc-* properties, so no @cssprop tags.

Motivation and context

Locks in the migrated behavior and the SWC-2295 adaptive-border logic with regression protection (answering the "no tests" feedback on #6443), and adds the Storybook docs page so the component is usable and understandable by others.

Related issue(s)

• Epic SWC-2137; a11y SWC-2295
• Follows feat(color-handle): scaffold 2nd-gen core/SWC structure (Phase 2&3) #6443 (Phases 2–5)

Verification

Local (Node 24.11.1): Vitest storybook project — 13 passed (5 play tests + 8 story smoke renders); Playwright a11y — 12 passed (3 browsers). yarn lint:docs-pages passes; Storybook shows a single color-handle docs entry (no duplicate). test-storybook aXe is blocked locally by an unrelated @swc/core native-binding failure + stray-worktree jest haste collision; aXe still runs in CI.

Out of scope / follow-ups

• Consumer-facing breaking-change and migration guidance (tag rename, --mod-* removal, fill property-vs-attribute) lands in the dedicated consumer migration guide, not the per-component MDX.
• Parent-embedded stories and full-spectrum contrast VRT come when a parent color picker (swc-color-area/-slider/-wheel) is migrated.

Author's checklist

• I have read the CONTRIBUTING and PULL_REQUESTS documents.
• I have reviewed the Accessibility Practices for this feature.
• I have added automated tests to cover my changes.
• I have included a well-written changeset if my change needs to be published. (Tests/docs only; no changeset.)
• I have included updated documentation (per-component MDX docs page).

Accessibility testing checklist

Color handle is a non-interactive visual primitive; name/role/value/keyboard belong to the parent picker. This PR adds the a11y regression tests and docs rather than changing behavior.

• Keyboard — no focusable parts on the handle itself (parent owns keyboard); confirm no focusable node is introduced.

  1. Open Storybook story Color Handle/Overview.
  2. Tab through the canvas.
  3. Expect the handle host to not receive focus / expose no role.

• Screen reader — handle exposes no role/name; built-in loupe SVG is aria-hidden.

  1. Open Color Handle/Accessibility.
  2. Inspect the accessibility tree.
  3. Expect no role/name on the host and the loupe SVG hidden.

[changeset-bot]

⚠️ No Changeset found

Latest commit: df98f04

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions]

📚 Branch Preview Links

• Documentation Site (first-gen)
• Storybook (first-gen)
• Storybook (second-gen)

🔍 First Generation Visual Regression Test Results

When a visual regression test fails (or has previously failed while working on this branch), its results can be found in the following URLs:

• Spectrum | Light | Medium | LTR
• Spectrum | Dark | Large | RTL
• Express | Light | Medium | LTR
• Express | Dark | Large | RTL
• Spectrum-two | Light | Medium | LTR
• Spectrum-two | Dark | Large | RTL
• High Contrast Mode | Medium | LTR

Deployed to Azure Blob Storage: pr-6465

If the changes are expected, update the current_golden_images_cache hash in the circleci config to accept the new images. Instructions are included in that file.
If the changes are unexpected, you can investigate the cause of the differences and update the code accordingly.