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598d12eb68
Two convergence bugs surfaced by the security review: - Role guard (finding B): processOffer accepted an offer even when we are the KEM initiator for the peer, and processAnswer accepted an answer when we are the responder. The KEM is unidirectional (initiator offers, responder answers), so a role-violating message is anomalous — a desync, a duplicate, or an injected/spoofed data-path packet. Processing it derived and committed a fresh PSK, overwriting a live one and silently dropping any in-flight exchange (whose retry loop then exited without raising a failure or re-bootstrapping). Reject offers when we are the initiator and answers when we are not; this drops only anomalous traffic and leaves the normal flow untouched. - Re-bootstrap on signal re-negotiation (finding A): SignalOffer was idempotent in stateAwaitingRekey too, replaying the frozen bootstrap offer. After the responder restarted and lost its state it derived a different PSK from fresh material, which our awaitingRekey side then rejected — a permanent desync with no recovery (in strict mode the peer stays blocked). Make the idempotency apply only while a bootstrap is still in flight (awaitingAnswer); once a PSK is derived, a fresh signal offer starts a new exchange so both sides converge. The controller-double-offer case the idempotency guarded is already covered by ShouldSendBootstrapOffer. Reusing the cached offer also reused the same ephemeral keys across exchanges, reducing forward secrecy. Both paths have a failing-without-the-fix regression test.