[discussion] Add Phone Number component?

# Feature request

## Summary

A phone number input with a country code selector.

## Examples in other libraries

- https://catamphetamine.gitlab.io/react-phone-number-input/
- https://shadcn-country-dropdown.vercel.app/phone-input
- https://github.com/viclafouch/mui-tel-input

## Motivation

Phone number inputs come in a lot of different styles yet usually hold the same logic,
select a country → write a number.

Could be nice having an unstyled component that helps handle the accessibility (screen readers, focus) of this component.

The issue names no files, tests, or entry points. Start by reviewing existing unstyled component patterns in the repository and the accessibility expectations for a country selector paired with a phone-number field. Done means an agreed component design exists and the resulting component supports country selection, number entry, screen-reader access, and focus handling.

Written by the indexing model from the issue text.