Function validate_final_core_result 

pub fn validate_final_core_result(
    schema: &AdmittedSchema,
    value: &Value,
    expected_result_type: FinalCoreResultType,
) -> ValidationResult

Validates a final core result against an admitted schema and its expected discriminator.

This is intentionally stricter than peer-result compatibility decoding: safe final emission must carry an explicit core resultType; absent, non-string, extension, and cross-branch values are rejected here.