Function wasm_host_shim 

pub fn wasm_host_shim(name: &str) -> String

The JavaScript host shim written beside an emitted .wasm — supplies every env.* import the backend can emit (the display sinks, the float display FMT_F64_JS, the scalar→Text formatters, parse_int, pow, and an args host that materializes process.argv as a Seq of Text in the module’s linear memory). Running it needs only a wasm engine (node/V8).