[accordion] disabled attribute isn't set on AccordionTrigger

# Bug report

## Current behavior

If I set the attribute `disabled` at `true` on AccordionItem, the AccordionTrigger (the button) only has the `aria-disabled` attribute or `data-disabled`.
So the button/trigger is still "keyboard focusable".

## Expected behavior

I attempt to see the `disabled` attribute added to the "button", not only the `aria-disabled` or `data-disabled` attribute.

## Reproducible example

[Shadcn/ui example](https://ui.shadcn.com/docs/components/base/accordion#disabled)

## Base UI version

v1.2.0

## Which browser are you using?

Chrome v145

## Which OS are you using?

Mac OS v15.5

## Additional context

The bug was detecting by using shadcn/ui with base-ui: https://ui.shadcn.com/docs/components/base/accordion#disabled