feat(tooltip): add pf-v6-tooltip element

[bennypowers]

Summary

• New pf-v6-tooltip element ported from v5 with v6 design tokens
• FloatingDOMController with arrow element positioning
• Cancellable TooltipShowEvent/TooltipHideEvent with reason enum for selective trigger prevention
• trigger attribute (IDREF) and property (Element ref) for external trigger elements
• entry-delay/exit-delay (default 300ms), alignment (start/end/left/right), position, no-flip, flip-behavior
• light-dark() CSS fallbacks for correct inverse color scheme
• ariaDescribedByElements wiring between trigger and tooltip content
• 9 demos: basic, placement, trigger-ref, trigger-element, slotted-content, dynamic-content, left-aligned, color-scheme, options playground
• 17 unit tests

Test plan

• Verify tooltip shows on hover and focus in all demos
• Verify tooltip hides on mouseleave, focusout, and Escape
• Verify light-dark color scheme inversion in color-scheme demo
• Verify external trigger via IDREF (trigger-ref) and Element ref (trigger-element)
• Verify alignment attribute changes text-align
• Verify entry-delay/exit-delay in options playground
• Verify no-flip disables repositioning
• Run /review-a11y, /review-api, /review-demos
• Visual parity with patternfly.org tooltip

Closes #3048

[changeset-bot]

🦋 Changeset detected

Latest commit: b52089b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@patternfly/elements	Minor

Not sure what this means? Click here to learn what changesets are.

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

[github-actions]

✅ Commitlint tests passed!

More Info

{
  "valid": true,
  "errors": [],
  "warnings": [],
  "input": "feat(tooltip): add pf-v6-tooltip element"
}

[github-actions]

✅ Deploy Preview for patternfly-elements ready!

Name	Link
🔨 Latest commit	d88bd77
😎 Deploy Preview	https://deploy-preview-3141--patternfly-elements.netlify.app/

---

To edit notification comments on pull requests, go to your Netlify site settings.

[github-actions]

SSR Test Run for 4e4a328: Report

[github-actions]

SSR Test Run for 6b79b33: Report

[github-actions]

SSR Test Run for d88bd77: Report

[bennypowers]

Cross-root aria-describedby limitation

The tooltip sets ariaDescribedByElements on the trigger to reference the shadow-internal #content div. This is the correct API for cross-root ARIA relationships, but it silently fails in all browsers today: the accessibility tree shows no describedby relationship.

Per the current spec, ARIA element reflection only works when shadow roots are in an ancestor/descendant relationship, and even then only in the shadow-to-light direction. Our use case (light DOM trigger referencing shadow DOM content) goes the wrong way. The WPT test explicitly asserts that cross-root refs produce an empty computed label.

This means tooltip triggers currently have no programmatic describedby relationship in any browser. The tooltip content is still announced when visible (via role="tooltip" and proximity in the accessibility tree), but there is no formal ARIA association.

The Reference Target proposal (Chrome origin trial) would solve the slotted trigger case. The external trigger case (sibling elements) would need the relaxation discussed in WICG/aom#192. Both whatwg/html#5401 and whatwg/html#10707 track the broader spec work.

Keeping the ariaDescribedByElements call as progressive enhancement -- it will start working once browsers ship a solution. No workaround attempted; the alternatives (hidden light DOM spans, aria-label mirroring) add complexity for a temporary gap.

@adamjohnson and @hellogreg -- could you verify the actual screen reader experience here? Want to confirm the tooltip content is still announced via proximity/role="tooltip" even without the formal describedby association.