[Menu]: a11y: ui5-menu popover exposes role="dialog" (aria-modal) instead of role="menu", inconsistent with an aria-haspopup="menu" opener #14219

Describe the bug

When a trigger button declares aria-haspopup="menu" and opens a ui5-menu, the opened popup is not exposed as a menu. ui5-menu renders its items in a ResponsivePopover whose inner section is role="dialog" with aria-modal="true", wrapping the role="menu" list. A screen reader therefore announces a "menu button" on the opener but encounters a dialog containing the menu — an inconsistent popup semantic (WCAG 4.1.2 Name, Role, Value; 1.3.1).

A consumer cannot fix this from outside the component: the ResponsivePopover lives in ui5-menu's shadow DOM, ui5-menu exposes no prop to change the popover role, and the PopupAccessibleRole enum only offers None | Dialog | AlertDialog (no Menu).

Root cause (source)

• Popup.accessibleRole defaults to "Dialog" — packages/main/src/Popup.ts:178 — which drives the section role="dialog" (_role) and aria-modal="true" (_ariaModal).
• MenuTemplate.tsx wraps List accessibleRole="Menu" in a ResponsivePopover without setting accessibleRole, so the menu's popover inherits the "Dialog" default.

Isolated example

Any Button with aria-haspopup="menu" as the opener of a ui5-menu with a couple of ui5-menu-items. Inspect the accessibility tree with the menu open.

Expected behaviour

The opened popup's role matches the opener's aria-haspopup="menu" — i.e. the only popup role exposed is the List's role="menu" with its role="menuitem" children; no competing role="dialog" / aria-modal wrapper.

Actual behaviour

Accessibility tree (desktop):

dialog "Select an option from the menu"  (aria-modal="true")   <-- ResponsivePopover section
  menu
    menuitem "..."
    menuitem "..."

Suggested fix

Have ui5-menu set its internal ResponsivePopover accessibleRole="None" (which makes _role and _ariaModal undefined) so the List's role="menu" is the sole exposed popup semantic. Popover focus management is handled by the focus-trap spans, so keyboard behaviour is unaffected.

Context

Found while verifying an SAP SuccessFactors accessibility defect: Approve/Decline "menu buttons" on the Home page open ui5-menu; aria-expanded toggles and role="menu"/role="menuitem" are present, but the popover wrapper is role="dialog". Related prior items: #9313 (Menu popover treated as a dialog, accessible name added), #6810 / #6090 (requests to allow a menu role on Popover).

UI5 Web Components version

2.x (reproduced on current main)