Extra unused files are output with bundleStrategy: 'single'

[danielcrabtree]

Describe the bug

As per the comment by @ligazetom in #3882, extra unnecessary and unused files are included in the build output when using the new bundleStrategy: 'single'.

In my case, I have a default new project using adapter-static with SSR disabled and tailwind. The generated entry point html correctly only contains references to the js and css bundles.

However, there is also a _layout css bundle generated that is unused and should not exist.

In addition, there is a env.js file, that is not referenced from anywhere and so apparently should not exist either.

Reproduction

Set bundleStrategy: 'single'.

Logs

System Info

npmPackages:
    @sveltejs/adapter-static: ^3.0.8 => 3.0.8 
    @sveltejs/kit: ^2.16.0 => 2.18.0 
    @sveltejs/vite-plugin-svelte: ^5.0.0 => 5.0.3         
    svelte: ^5.0.0 => 5.22.5
    vite: ^6.0.0 => 6.2.0

Severity

annoyance

Additional Information

No response

[shfx]

I've noticed that moving css import from +layout.svelte to hooks.client.ts fixes the issue.