[Request] Support for portable stories and experimental vitest-addon

[bhvngt]

As storybook 8.3 is out with experimental support for running portable stories with vitest.

This is a feature request for supporting svelte-native csf with vitest-plugin. This will also enable this plugin to support exportable portable stories.

[xeho91]

@JReinhold

Do we want to try to solve this case before the major release?

You once asked me if it was necessary to provide the enforce: "post" option for Vite transform plugin.
I'm exploring this quickly, and removing this option doesn't break anything. I've tested on dev and build modes.

Is that the only thing that was the blocker, or is there anything else?