template_component_uncalled

What happened

A function named like a component is bound as a template's content without being called, as ${AddItem}, which the renderer cannot display; zerolith lint and the Vite plugin report it before the code runs, since the type checker cannot tell it from an event handler.

What to do

Call it, as ${AddItem()}, or write in JSX.

The arguments of the specific occurrence are in the query string of the URL the error gave you.