PSBT/MuSig2 coordination over Nostr relays: transport invariants for nonce safety under at-least-once delivery

When considering the reliability of wallet applications from a user's perspective, it is crucial to understand how the system handles failures. For instance, if a relay in the system goes offline or accidentally sends a duplicate message, the repercussions on the wallet's functionality are significant. Users need to know whether the wallet can autonomously recover from such incidents or if they must manually restart the signing session. Providing transparent information about the status of the wallet and detailed recovery steps is essential for building user trust, especially when dealing with substantial amounts of money. This assurance is vital as users are more likely to rely on technology that clearly communicates its fail-safes and recovery mechanisms in scenarios of failure.