Error creating and opening a database

I'm building a svelte 5 app, have installed sql.js and downloaded the sql-wasm.warm and worker.sql-wasm.js. Whenever I try and create or open a database I get an uncaught in promise error. I'm hoping to create a client side database that doesn't get wiped when the browsers data is wiped.
ChatGPT says it's possible, but I've not been able to get the code working at all in svelte (5 is still between by the way)...

Start with the Svelte 5 app's sql.js initialization and the downloaded sql-wasm.warm and worker.sql-wasm.js files; reproduce the uncaught promise error and inspect the browser console and loading behavior. Done means the app can create or open a database without the error, with the intended persistence behavior demonstrated or documented.