ReplayedNonceException

Thrown by a signed {@see \Milpa\Live\Contracts\Transport\StateTransferCodecInterface} decorator when an otherwise cryptographically valid envelope's nonce has already been consumed by a prior call — i.e. the envelope was not tampered with, but this exact signed request has already been acted on once and is being replayed (captured and resubmitted, deliberately or not). A `\RuntimeException` subtype specifically so callers such as {@see \Milpa\Live\Http\LiveEndpoint} can distinguish "this request was * already processed" from an ordinary signature/tamper failure and report a different status for it, while still satisfying the interface's `@throws \RuntimeException` contract for callers that only care that decoding failed.