Audit of the crew Chat tab (see CREW_CHAT_AUDIT.md):
- A sent crew message never appeared: useSendDirectMessage invalidated the list
keys but not ['group-messages', gid, ...] (the thread key). Now optimistically
inserts the sender's own plaintext (no refetch -> no Amber pop-ups).
- Every reader decrypted every wrap under its own query key, so each view
(Messages, then each crew thread) re-decrypted the whole inbox. Added a shared,
coalesced, bounded session decrypt cache (decryptGiftWrap), successes only.
- Threads dedup by rumor id; CrewChat guards double-send with a ref; the Cordn
path optimistically inserts and invalidates only for silent signers.
