fix(Select/List): improvedA11y combobox VPAT fixes (Hub #242, #391, #392)

[agupta-eightfold]

Summary

Fixes three WAI-ARIA APG combobox a11y defects confirmed live on QA (Allyant Hub #242, #391, #392), all rooted in the shared Select/Menu/List components in improvedA11y mode. A single library fix resolves them for every improvedA11y Select consumer (TemplateSelectModal, TimeSlotSelect, and any other usage).

1. Listbox missing accessible name (#391)

List destructured only aria-label and applied it to the <ul>/<ol>; aria-labelledby fell into ...rest and landed on the outer wrapper <div> instead of the role="listbox" element. Consumers passing aria-labelledby via menuProps (e.g. TimeSlotSelect) got a listbox with no accessible name. Now forwarded to both <ul> and <ol> alongside aria-label.

2. aria-selected doesn't follow keyboard focus (#392, #242)

aria-selected was set once from the committed value (opt.selected) and never moved as Arrow keys changed the active descendant, so focus and selection state diverged. Per the APG Combobox pattern ("selection follows focus in the listbox"), single-select listboxes now track the active descendant. Multi-select listboxes keep aria-selected on the committed choices (guarded with !multiple) — moving it with focus there would be incorrect.

3. VoiceOver never announces the highlighted option (#392, #242)

The visually-hidden live region reacted only to dropdownVisible/options/searchQuery/selectLocale, never to activeDescendantId, so VoiceOver announced only "expanded" and nothing as the user arrowed through options (NVDA compensates via native aria-activedescendant). The active option's text and position are now announced.

⚠️ Reviewer flag: this causes NVDA to hear the option name twice (once natively via activedescendant, once via this echo) — accepted tradeoff for VoiceOver support.

The "of" connector in the announcement ("Apple, 1 of 3") is localizable via a new optional optionPositionSeparatorText locale key (set on en_US/en_GB; other locales fall back to "of" in code pending translation).

Test plan

• New unit tests for all three fixes (List: attr lands on list el not wrapper; Select: selection-follows-focus single-select, multi-select unchanged, live-region echo on arrow nav).
• npx jest src/components/List src/components/Select src/components/Menu → 122 tests pass, snapshots clean.
• Verified end-to-end chain: menuProps.aria-labelledby → Select restMenuProps → Menu ...rest → List → <ul role="listbox">.

Consumer impact

No app-side code changes needed. vscode consumers already pass correct attributes; they only need to bump @eightfold.ai/octuple after this releases.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.99%. Comparing base (14cf524) to head (3cb8446).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1149      +/-   ##
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+ Coverage   84.97%   84.99%   +0.01%     
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  Files        1230     1230              
  Lines       21542    21553      +11     
  Branches     8185     8191       +6     
==========================================
+ Hits        18306    18318      +12     
+ Misses       3150     3149       -1     
  Partials       86       86              

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[agupta-eightfold]

Tracked in ENG-202332 — https://eightfoldai.atlassian.net/browse/ENG-202332 (TA Everest - Sprint 40).