Function validate_file 

pub fn validate_file(
    file: &str,
    inputs: &[String],
) -> Result<Vec<(String, Diag)>, i64>

single-file validation, module-aware like check and evaluate: load the universe, check every module, then evaluate with the --input documents bound (none bound is fine: fallbacks apply). Diagnostics come tagged with the file each is reported against; Err carries a usage exit code as a negative