86da52acc4
Protocol (sender_keys.rs): - SenderKey: symmetric key with chain ratchet (forward secrecy per chain) - generate(), rotate(), encrypt(), decrypt() - SenderKeyDistribution: share key via 1:1 encrypted channel - SenderKeyMessage: encrypted group message (O(1) instead of O(N)) - Chain key ratchets forward on each message (HKDF) - Generation counter for key rotation tracking - 4 tests: basic, multi-message, rotation, old-key rejection WireMessage: - GroupSenderKey variant: encrypted group message - SenderKeyDistribution variant: key sharing Server: dedup handles new variants. CLI TUI + recv: stub handlers for new message types. 23/23 protocol tests pass. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>