The default export declaring in .d.cts is not accurate.

[kricsleo]

Environment

Node.js: *
unbuild: v3.0.1

Reproduction

https://stackblitz.com/edit/vitejs-vite-t55rnaxz?file=package.json,tsconfig.json,build.config.ts,src%2Findex.ts,dist%2Findex.d.cts&terminal=dev

Describe the bug

First run build, this will emit the cjs output.

The source index.ts only contains a default export:

export default function add(): number {
  return 42
}

In the index.cjs output, there is only the default export (this is correct ✅):

module.exports = add;

But the index.d.cts output, it's:

export { add as default };

this is wrong ❌, because this would lead to ❗️ Incorrect default export . You can run check to verify this problem.

And it should be:

export = add;

Another build tool tsup could have encountered the same problem, but they introduced a fix for this:
https://github.com/egoist/tsup/blob/cd03e1e00ec2bd6676ae1837cbc7e618ab6a2362/src/rollup.ts#L92-L109

They manually replaced this from export { XXX as default }; to export = XXX;

I'm wondering if we could do the same for unbuild ❤️.

(If that's the solution, I can popup a PR for it 🙌🏻)

Additional context

No response

Logs

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