Turbopack `require.context` ESM interop is different compared to Webpack

Originally reported by @Vinnl in https://github.com/vercel/next.js/pull/78148#issuecomment-2821067072

Link to the code that reproduces this issue

https://github.com/Vinnl/tmp-repro-next-turbopack-require-context/commit/0878b97d96e1fdb8c7478531787073fb57e6f0b1

To Reproduce

1. Run npm run dev
2. Visit http://localhost:3000/
3. Observe the console (not the browser console), see "File contents\n" in the logs.
4. Terminate the process, then run npm run dev-turbo
5. Visit http://localhost:3000/

Current vs. Expected behavior

What happened:

I saw {"default":"File contents\n"} in the logs.

What I expected:

See "File contents\n" in the logs, just like with the Webpack build.

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP PREEMPT_DYNAMIC Thu Apr 10 21:50:55 UTC 2025
  Available memory (MB): 15691
  Available CPU cores: 8
Binaries:
  Node: 20.11.0
  npm: 10.2.4
  Yarn: 1.22.19
  pnpm: 9.4.0
Relevant Packages:
  next: 15.4.0-canary.2 // Latest available version is detected (15.4.0-canary.2).
  eslint-config-next: N/A
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.8.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Turbopack

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

No response

Start with the linked reproduction commit and run its npm run dev and npm run dev-turbo commands, comparing the server console output for require.context. Trace the Turbopack path involved in ESM interop and compare it with the Webpack behavior. Done means both commands log "File contents\n" rather than the default-object form.