shipping 5MB of JS to the client
Yes. Once. For a single page web app. To avoid the latency and bandwidth of shipping another page ever again. Even 5MB, as large as that is, loads in a fraction of a second. And once it is loaded, the whole application is ready to go…
It's much easier to add reactivity to your application through Vanilla JS or something like Alpine.js than it is to maintain 2 codebases and an API contract.
Ok that is a good point - I hadn’t looked into AlpineJS, which does seem like a good option if you wanted some interactivity in minimalist web app. An API is a critical development of most any modern web app regardless.
That being said, I think we have different things in mind when it comes to what is production grade. Separating the front end server from the backend server is quite standard as far as I know. I recognize your points but, all the same, let’s agree to disagree.
Anyhow, this discussion isn’t too relevant to what OP is looking for, which is a local executable option.