Function check 

pub fn check(source: &str, main_path: &str, root: &Path) -> CheckOutcome

Check one .opy project: preprocess (includes/defines) → parse (CST) → resolve (Opy HIR). main_path is the display path recorded in the file registry; root is the include base. No Workshop backend is required; settings blocks are validated against the canonical emission table so the check verdict agrees with compile on settings keys (issue #411).