[toggle] Single selection mode with role="radio"

Hello team!

Congrats on your first stable release!

My question is around the Toggle/ToggleGroup components in their single selection mode.

As per [this example in shadcn](https://ui.shadcn.com/docs/components/toggle-group#single), Radix `ToggleGroup` sets `role="radio"` to `ToggleGroupItem`'s in single selection mode and I was kind of expecting the same from Base UI `ToggleGroup` when `multiple={false}`.

I see the same behavior in React Spectrum [ToggleGroup](https://react-spectrum.adobe.com/react-aria/ToggleButtonGroup.html#single-selection)

Is there a reason we are not doing the same on the Base UI component?

TIA!