htmx is built to mutate html from the backend based on server side events. I'm not going to say it is better or worse than svelte for your use case but how you are describing it here is selling it short. I suspect you could make a decent files app with htmx and a sprinkle of JavaScript.

As per your development process, if you use htmx you can serve the template files from disk. Then all you need to do is edit the html templates which your backend reads in. No need to rebuild your golang application. For some changes you wouldn't have to reload the page just click the interaction to get the html fragment from the server.

You would need to rebuild your go application if you are changing parameters input into the template but that is conceptually the same as a client side template needing an API change. This also requires a rebuild.