- RecoversViaResignalAfterDataPathBreak: a data-path rotation that can no longer
converge raises OnRekeyFailed, and re-bootstrapping over signalling resyncs both
peers on a fresh PSK even while the data path stays broken.
- ConcurrentRekeysNoRace: hammers the single-lock state machine with concurrent
rotation clocks from many goroutines (run with -race) and asserts no split-brain
via a final deterministic bootstrap.