Hovering over the link applies CSS effects

Describe the bug

Summary

Hovering a link of a page which imports CSS file with css variables, override current page css variable.

We have this issue since version @2.48.0.

Details

+layout.svelte in each sub routes, import a different css for each different css variable. (In use case, each sub directory have different own brand color).

CSS is stored in /static folder and import like

<svelte:head>
	<link href="./sub_a.css" rel="stylesheet" />
</svelte:head>

When hover a link to page, preload data is triggered.
However, css variable changed as well.
It used to not be like that before.

https://github.com/user-attachments/assets/03becd2e-0a6d-4280-a512-3ae355c31f2a

Expectation

css variable should not change on hovering the link.

Reproduction

https://www.sveltelab.dev/4302565mia8i8jy

Logs

System Info

System:
    OS: macOS 14.6.1
    CPU: (10) arm64 Apple M2 Pro
    Memory: 70.28 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
Binaries:
    Node: 22.17.0 - /Users/mymachine/.nodenv/versions/22.17.0/bin/node
    Yarn: 1.22.22 - /opt/homebrew/bin/yarn
    npm: 10.9.2 - /Users/mymachine/.nodenv/versions/22.17.0/bin/npm
    pnpm: 10.4.1 - /Users/mymachine/.nodenv/versions/22.17.0/bin/pnpm
    bun: 1.2.9 - /opt/homebrew/bin/bun
Browsers:
    Chrome: 143.0.7499.41
    Safari: 17.6
npmPackages:
    @sveltejs/adapter-auto: 7.0.0 => 7.0.0 
    @sveltejs/adapter-cloudflare: 7.2.4 => 7.2.4 
    @sveltejs/enhanced-img: 0.9.2 => 0.9.2 
    @sveltejs/kit: 2.48.0 => 2.48.0 
    @sveltejs/vite-plugin-svelte: 6.2.1 => 6.2.1 
    svelte: 5.45.8 => 5.45.8 
    vite: 7.2.6 => 7.2.6

Severity

annoyance

Additional Information

No response

Reproduce the behavior from the linked SvelteLab example, focusing on the per-route +layout.svelte links to CSS files in /static and the hover-triggered preload. Compare behavior with the reported change from @2.48.0, then verify that hovering a link no longer changes the current page's CSS variable.