Function map_source_error 

pub fn map_source_error(wasm_err: WasmError) -> WasmError

Map a source-world WIT WasmError to the canonical crate-level WasmError.

Mirrors map_plugin_error for the source binding namespace. Needed so the submit-exchange drain (drain_guest_stream) can map the source world’s terminal-future error into a CamelError via E: Into<CamelError>.