Assets path not replaced by _svelte_kit_assets in preview

Describe the bug

One of the stated use cases for the config.kit.paths.assets config var is for the case where assets will be hosted on a separate domain to the site itself.

The docs state:

If a value for config.kit.paths.assets is specified, it will be replaced with '/_svelte_kit_assets' during vite dev or vite preview, since the assets don't yet live at their eventual URL.

That is what happens with vite dev. When running vite preview however, the value from config is still used. The only relevant previous issue I could find is #1154.

Reproduction

https://github.com/drzax/assets-repro

Logs

No response

System Info

System:
    OS: macOS 14.4.1
    CPU: (12) arm64 Apple M2 Max
    Memory: 839.94 MB / 32.00 GB
    Shell: 5.2.26 - /opt/homebrew/bin/bash
  Binaries:
    Node: 21.7.1 - /opt/homebrew/bin/node
    npm: 10.5.0 - /opt/homebrew/bin/npm
    pnpm: 8.15.7 - /opt/homebrew/bin/pnpm
    bun: 1.0.36 - /opt/homebrew/bin/bun
  Browsers:
    Chrome: 124.0.6367.119
    Edge: 124.0.2478.67
    Safari: 17.4.1
  npmPackages:
    @sveltejs/adapter-auto: ^3.0.0 => 3.2.0
    @sveltejs/adapter-static: ^3.0.1 => 3.0.1
    @sveltejs/kit: ^2.0.0 => 2.5.7
    @sveltejs/vite-plugin-svelte: ^3.0.0 => 3.1.0
    svelte: ^4.2.7 => 4.2.15
    vite: ^5.0.3 => 5.2.10

Severity

blocking all usage of SvelteKit

Additional Information

We need to be able to debug production builds locally and this is currently blocking that.

Start with the linked assets-repro reproduction and compare how config.kit.paths.assets is handled by vite dev versus vite preview. Done means vite preview replaces the configured asset path with /_svelte_kit_assets, matching the documented behavior.