Nice! I'm working on a similar language in some ways.

One decision I made is to specifically not compile to JS. JS/Wasm interop is good enough with Wasm GC that I made the choice to focus on Wasm-only constraints and semantics and not worry about how things like the types being wrong, or how ints translate to JS, how to handle null vs undefined, etc. JS GCs collect objects and cycles across the Wasm boundary, and with the JS string built-ins you can handle strings efficiently.

I couldn't load your demo, btw.