sandboxDarkClass does not work when using grid layout

[valgeirb]

Describe the bug

According to this comment, an iframe is not used when using a grid layout. The problem is that then the sandboxDarkClass won't get toggled.

This makes using the grid layout impossible if you want to show dark versions of your components.

Reproduction

Define a dark class for easier debugging:

defineConfig({
  sandboxDarkClass: 'my-dark-class',
})

Notice that the class does not get added when using a grid layout.

System Info

System:
    OS: macOS 13.1
    CPU: (8) arm64 Apple M1 Pro
    Memory: 1011.77 MB / 32.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.14.2 - ~/.volta/tools/image/node/16.14.2/bin/node
    Yarn: 1.22.18 - ~/.volta/tools/image/yarn/1.22.18/bin/yarn
    npm: 8.5.0 - ~/.volta/tools/image/node/16.14.2/bin/npm
  Browsers:
    Chrome: 109.0.5414.119
    Firefox: 107.0.1
    Safari: 16.2
  npmPackages:
    @histoire/plugin-vue: ^0.13.2 => 0.13.2 
    @vitejs/plugin-vue: ^4.0.0 => 4.0.0 
    histoire: ^0.13.2 => 0.13.2 
    vite: ^4.0.4 => 4.0.4

Used Package Manager

npm

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