feat(menu): allow overriding the popover role

[kelsos]

Closes #564

Problem

RuiMenu hardcoded role="menu" on its teleported popover, with no attrs spread and no prop to change it. RuiMenu is the popover primitive for things that are not menus, and the container role forces the ARIA model: a listbox cannot nest inside a menu, so an input that opens one cannot legitimately be a combobox.

Change

• New role prop on RuiMenu: 'menu' | 'listbox' | 'tree' | 'grid' | 'dialog', defaulting to 'menu'.
• The activator wrapper's aria-haspopup is derived from it so the two agree. For the default it still emits aria-haspopup="true", which is equivalent to "menu", so existing callers and their tests see no change.
• RuiMenuRole is exported from the components entry.
• Storybook control + unit tests for the default, a custom role, and the matching aria-haspopup.

<RuiMenu role="listbox">
  <!-- role="option" rows, opened by a role="combobox" input -->
</RuiMenu>

Notes

The library's own selection components (RuiAutoComplete, RuiMenuSelect, ...) still use the default menu role. Moving them to the listbox/combobox model is a larger change (option roles, aria-activedescendant, aria-selected) and is left out of this PR.

Testing

• pnpm run test:run (1346 passing)
• pnpm run typecheck
• pnpm run lint (no new warnings)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.04%. Comparing base (36f6b59) to head (2d00877).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #565   +/-   ##
=======================================
  Coverage   87.04%   87.04%           
=======================================
  Files         159      159           
  Lines        6306     6307    +1     
  Branches     1938     1939    +1     
=======================================
+ Hits         5489     5490    +1     
  Misses        817      817           

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