Function translate_diagnostics 

pub fn translate_diagnostics(
    diagnostics: &[RustcDiagnostic],
    source_map: &SourceMap,
    interner: &Interner,
) -> Option<LogosError>

Translates rustc diagnostics to LOGOS errors.

Returns the first successfully translated error — the CLI’s one-error-at-a-time contract. IDE surfaces want translate_diagnostics_all.