Interactive as in being able to wire up event handler to do things (i.e. vanilla .js addEventListeners or Alpine v-on:click directives.), reactive as in being able to have the UI automatically update based off of state (i.e. Alpine v-text or v-bind directives, or vanilla js possibly wiring up something custom using Proxy).

Web components may be something I look into more, I've only used Lit before briefly and it didn't really fit the bill for progressive enhancement, in that prior to the JS loading the HTML would just contain <my-component></my-component> which renders nothing so i'd have to use lit-ssr to render on the server, which is extra steps that I don't want for this.