a11y: Tabs — tabs and tabpanels are not programmatically associated; other APG tabs-pattern deviations

Context

Found during the 2026 Axim-commissioned accessibility audit of Paragon, while documenting Tabs against the APG tabs pattern.

Current behavior (from src/Tabs/__snapshots__/Tabs.test.jsx.snap and React-Bootstrap 1.6.5)

1. No tab↔panel association. Tab panels render role="tabpanel" with aria-labelledby={null}, and tabs render role="tab" with no aria-controls (no id linkage in either direction).
2. No roving tabindex. Every tab is an <a href="#"> and remains in the page tab sequence; the APG pattern expects a single tab stop for the tablist with arrow-key navigation inside. Arrow keys do work (React-Bootstrap AbstractNav: Left/Up previous, Right/Down next, selection follows focus), but Home/End are unsupported and Space does not activate (anchor semantics).
3. Overflow "More..." control. The responsive overflow renders a <button aria-haspopup="true"> nested inside an <a role="tab"> that has no aria-selected — nested interactive elements, and a tab that isn't a tab. Hidden tabs are exposed as dropdown items rather than tabs.

Impact

• (1) Screen reader users landing in a panel get no announcement of which tab labels it; some AT navigation shortcuts between tab and panel don't work. WCAG 1.3.1 Info and Relationships, 4.1.2 Name, Role, Value.
• (2) Extra tab stops slow keyboard traversal of pages with many tabs; missing Space activation is inconsistent with the announced role.
• (3) The nested-interactive structure produces unpredictable focus/announcement behavior in the overflow case.

Suggested direction

Generate stable ids per tab/panel and wire aria-controls/aria-labelledby (fixes 1 without behavior change); consider roving tabindex and Home/End as a follow-up; rework the overflow control so the "More..." toggle is not inside a role="tab" element.

References

• APG tabs pattern: https://www.w3.org/WAI/ARIA/apg/patterns/tabs/
• Related ACT rules: ARIA required context role, ARIA required owned elements, Element with role attribute has required states and properties

Start with the current behavior captured in src/Tabs/snapshots/Tabs.test.jsx.snap and the React-Bootstrap AbstractNav keyboard behavior. Implement stable tab/panel ids with aria-controls and aria-labelledby, then address the roving-tabindex and overflow-control deviations described in the issue. Done means the Tabs markup follows the referenced APG relationships without nested interactive controls.