The build command should output a standalone file (with possibly a few non-essential files).
The intermediate files should all be somewhere in the.svelte-kit directory.

It looks like something is off in your case. Maybe the library has something to do with it, not sure.

Ideally create a minimal reproduction and ask a separate question, providing all the necessary files.

Is it SSG or SPA? Is SSG possible?

It's fully static, see e.g. the linked example further up.

https://svelte.dev/docs/kit/configuration#router

What type of client-side router to use.

'pathname' is the default and means the current URL pathname determines the route
'hash' means the route is determined by location.hash. In this case, SSR andprerendering are disabled. ...

Does that mean that it is SPA?
I don't understand the rationale behind the use ofhash router type instead of the usualpathname.

It effectively is an SPA, though most SPAs would still pull data from some server instead of rendering it into the page on the server. Here the entire static application is in a single file, which requires hash-based routing.

I don't know if the inline bundle strategy can work without this, i.e. having it generatemultiple independent HTML files that inline their own JS & CSS. I suspect that this is not possible, though.