Invalid stub file generated for modules using abitrary module namespace identifier names

[sapphi-red]

Environment

Node 22.15.0
unbuild 3.4.0

Reproduction

https://stackblitz.com/edit/node-eufscqik?file=index.ts&terminal=dev

Describe the bug

For a module using arbitrary module namespace identifier names feature (tc39/ecma262#2154), unbuild generates a stub file that is not valid.
An example of the output is:

export const 'module.exports' = _module.'module.exports';

This feature is used for module.exports export feature as a part of require(esm) (nodejs/node#53848).

Additional context

No response

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