exportToStl function
Writes document as binary STL, reads the result back and compares.
A surface-count difference is expected, not a bug, the moment
document holds more than one: STL has no boundary between surfaces,
so StlWriter.warnings already says so, and ExportReport.differences
will report the merge as well — the two are meant to be read together,
not as a pass/fail on their own.
Implementation
Future<ExportReport> exportToStl(
ModelDocument document, {
String name = 'model',
}) => exportChecked(document, const StlModelWriter(), name: name);