Cannot import from a type-only package

[FelixGirard]

Describe the bug

I have a type-only package. We are importing from it and building successfully.
When vitest encounter that imports, it fails with the error:
Failed to resolve entry for package "@types/packageName". The package may have incorrect main/module/exports specified in its package.json.

Reproduction

Here is a small reproduction using @types/base64-js:

https://stackblitz.com/edit/vitest-dev-vitest-tcivys?file=test%2Fbasic.test.ts

System Info

System:
    OS: Windows 11 10.0.22631
    CPU: (20) x64 12th Gen Intel(R) Core(TM) i7-12800H
    Memory: 10.15 GB / 31.67 GB
  Binaries:
    Node: 18.20.2 - C:\Program Files\nodejs\node.EXE
    npm: 10.5.0 - C:\Program Files\nodejs\npm.CMD
    pnpm: 9.12.1 - C:\Program Files\nodejs\pnpm.CMD
  Browsers:
    Edge: Chromium (127.0.2651.74)
    Internet Explorer: 11.0.22621.3527
  npmPackages:
    @vitest/coverage-istanbul: 2.1.2
    vitest: 2.1.2

Used Package Manager

pnpm

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