It's not a website, it doesn't run in your normal browser. It runs as a standalone application.
> Why not? Why do you want a local first app in the first place? What's the purpose of a local first app, if not security?
Because as soon as those keys aren't available (either because the endpoint no longer exists, or you cannot connect to the endpoint for whatever reason (like being offline)), you can no longer access your data.
That isn't "local first" at all, it's something else entirely.