The area you're covering is closely related to an active area of development within the JS frontend framework community. They consider it hydration perf work and the working terminology is partial hydration or resumption/resuming rendering (there's a couple approaches/tradeoffs). In particular, the Marko team has a system under development that works this way without explicitly defined client/server pieces. They're mostly solving it on the server and streaming the HTML down since they have a priority on page load perf but the models look very close to me. I don't have a definitive piece to link as an intro and the concepts haven't made their way into the broader JS community but I thought you might be interested.
I'm happy that hyperfiddle is still going, I recall the Clojure NYC presentation and this is looking a lot more polished.