I'm seeing an issue where CSS is incorrectly loaded from other layouts.

I reproduced the issue in a repo.

Reproduction steps:

1. Create two routes simple and other and configure them to use layouts Layout.svelte and Other.svelte, respectively.
2. Create two CSS files, simple.css and other.css. Inside the script tag of each layout, import their respective CSS file.
3. Bug: Start the dev server and navigate to one of your routes. You'll see that on both routes, both simple.css and other.css are loaded.
   - Expected behaviour: On the simple route, only simple.css is loaded. On the other route, only other.css is loaded.