Source maps

The NAPI transform exposes a boolean sourcemap option and returns a parsed v3 map object; it does not expose input-map, inline/external, output-filename, or sourcesContent controls (options, public shape).

The builder uses the transform filename as its source and always records original source content (builder, compiler path); original byte offsets and generated UTF-8 positions are converted to source-map UTF-16 columns (original positions, generated positions).