Reproduction link or steps

https://stackblitz.com/edit/github-11wamky2?file=tsdown.config.ts

What is expected?

dist/index.d.{cts|mts}
dist/adapters/foo/index.d.{cts|mts}

What is actually happening?

dist/index.d.{cts|mts}
dist/index2.d.{cts|mts}

Any additional comments?

Trying to move trpc to using tsdown here: trpc/trpc#6789