Second production slice: the concrete Nostr backend on the shared connection,
using the vetted nostr package's crypto (NIP-44 spec-vector tested, gift wrap).
- NostrConnection: one dart:io WebSocket + identity + EVENT/OK, REQ/EOSE via
the library's Event/Filter/Request. Pure Dart, no Flutter.
- NostrOfferTransport (NIP-99 kind 30402) + Nip99Codec: geohash coarsened to a
NIP-52 prefix ladder on the wire; Offer stays inventory/location-agnostic.
- NostrMessageTransport (NIP-17): send/inbox via the library's DirectMessage
gift-wrap onion.
- NostrTrustTransport (custom addressable kind 30777): certify/revoke/discover.
- MiniRelay test support + integration tests: offers, messaging (metadata
privacy), WoT membership + revoke, and trust-filters-offers — all over ONE
shared connection, hermetic in-process relay.
Renamed the core offer lifecycle enum OfferStatus -> OfferLifecycle to avoid
colliding with app_seeds' sharing-intent OfferStatus (no Block 1 code touched;
app_seeds analyzes clean, 0 errors). commons_core: 55 tests green.
