Function classify_cargo_failure 

pub fn classify_cargo_failure(
    stderr: &str,
    stdout: &str,
) -> (ErrorClass, String)

Classify a cargo failure output into retry semantics for publish decisioning.

This is a hint, not authoritative truth. The returned ErrorClass is produced by pattern-matching on cargo’s human-facing stdout/stderr — a surface that is explicitly not a stable machine protocol. The retry loop consumes this classification as fast-path input, but the authoritative resolution for an ErrorClass::Ambiguous outcome comes from querying the registry (sparse index + API) via the reconciliation flow — never from the cargo text alone. See the ErrorClass rustdoc and shipper::engine::parallel::reconcile for the “hint vs truth” contract.