What problem does this feature solve?

Rsilb has build js api. But cannot get compiled stats object for returned instance after first compiled.
I tried onAfterBuild hook is still not works.

import { build } from '@rslib/core'

const instance = await build(/*..., config and options*/)

instance.stats // undefined
instance.onAfterBuild(options => {
  // not called when first compiled
})

What does the proposed API look like?

instance.stats // is a object
// or
instance.onAfterBuild(options => {
  // should called when first compiled
})

It's better to expose stats for buildInstance or allow developer to register hook before run rsbuildInstance.build.