scope(...).export() does not preserve the name of a type used for the scope's parameter if one is explicitly defined

[Dimava]

🧑‍💻 Repro

import type { Scope } from 'arktype'
import { scope } from 'arktype'

const _$ = scope({
  username: 'string.alpha',
})
type Identity<T> = T
export interface $ extends Identity<typeof _$.t> { }
export const $ = _$ as any as Scope<$>

const x = $.type('username')
//    ^?
// const x: Type<string.alpha, $>
const y = $.export().username
//    ^?
// const y: Type<string.alpha, { username: string.alpha; }>