Move m.mu.RUnlock to defer in GetCheckout and remove duplicate RLock/RUnlock around m.completed lookup. This prevents a deadlock when CheckoutPending error is returned but the RLock was already released. Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>