vitest-pool-workers does not run Wrangler custom builds

[GregBrimble]

What versions & operating system are you using?

wrangler 4.22.0, vitest 3.1.4 and @cloudflare/vitest-pool-workers 0.8.48

Please provide a link to a minimal reproduction

No response

Describe the Bug

When configuring vitest-pool-workers, pointing at a Wrangler config file which relies on a custom build does not work. I'd expect the custom build to run, but it does not.

Please provide any relevant error logs

No response