Function classify_baseline_value 

pub fn classify_baseline_value(
    value: &Value,
    expected: BaselineKind,
) -> BaselineFileKind

classify_baseline_file for a caller that parses the file itself.

The dead-code read needs both this answer and the deserialized struct, and its format is the one with required fields, so it parses once into a value and asks here rather than paying for a second parse of the same bytes.