[Menu] [Select] [Checkbox] [Switch] [RadioItem] provide focusableWhenDisabled

# Feature request

## Summary

Expose `focusableWhenDisabled` as a public prop on `Menu.Trigger`, `Select.Trigger`, `Checkbox.Root`, `Switch.Root`, and `Radio.Root` (and any other standalone trigger/input components that currently render with the native `disabled` attribute or `tabIndex={-1}` when disabled).

The mechanism already exists internally - `useFocusableWhenDisabled` is used by `Tab`, `Menu.Item`, and `Select.Item`, where it is hardcoded to `true` because composite items need to remain navigable. We would like the same toggle available on top-level controls, so consumers can opt into the same behavior.

When enabled, the component should render `aria-disabled="true"` instead of the native `disabled` attribute (for native button variants), and keep `tabIndex` at its default value of `0` (for non-native variants like `` in Checkbox/Switch/Radio). Click and keyboard activation should remain blocked by `useButton`, exactly as today.

## Motivation

Browsers skip elements with the native `disabled` attribute entirely in the tab order. This is technically spec-compliant, but it has a real accessibility cost:

- Screen reader users cannot discover disabled controls via keyboard.
- WCAG 4.1.2 (Name, Role, Value) requires that state changes be exposed to assistive technologies. The `disabled` attribute exposes the state - but only if the user can actually focus the element.

The current workaround is to use the `render` prop and strip the `disabled` attribute manually:

```tsx
{
const { disabled: nativeDisabled, ...rest } = props;
return ;
}}
/>
```

This works but is fragile, easy to forget, and requires every consumer to know the internal DOM output. Exposing `focusableWhenDisabled` as an opt-in prop would let teams adopt the modern ARIA practice.

A reasonable API:

```tsx
...

```

Default could stay false to avoid a breaking change.

Thanks for considering.

Start by tracing useFocusableWhenDisabled in Tab, Menu.Item, and Select.Item, then inspect Menu.Trigger, Select.Trigger, Checkbox.Root, Switch.Root, and Radio.Root alongside useButton. Add the opt-in behavior while preserving the current default: native variants should expose aria-disabled, non-native variants should remain focusable, and activation must stay blocked when disabled.

Written by the indexing model from the issue text.