# Milestone 6 — Discovery provider seam

## What landed

- `varde_daemon::discovery` with the spec's `DiscoveryProvider` trait,
  `TopicKey`, and the signed `Announcement` type. Signatures are ed25519
  (the same key type as iroh NodeIds) over a deterministic postcard
  encoding that includes the topic, so announcements can't be replayed
  onto other channels. Verification tests cover round trip, tampered
  root, wrong topic, forged author, mismatched signing key, and
  serde-then-verify.
- `LanDiscovery` implements the trait: mDNS sightings become
  locally-authored, signed announcements ("peer N may hold pinned root
  R"), one per pinned root. `announce()` is a no-op on the LAN — mDNS
  already advertises presence, and varde never broadcasts content lists.
- The daemon's auto-sync was refactored *onto* the seam: sightings feed
  presence tracking and the LanDiscovery channel; a single
  `on_announcement` path verifies, indexes, and applies the consent
  tiers (trusted author → pinned + incomplete → trusted providers →
  fetch). The milestone-4 mdns integration test passes unchanged through
  the new path, which is the proof the seam carries real traffic.
- Announcements surface on the event stream (`announcement` events) and
  are indexed in memory per root.
- `docs/redoal-integration.md` sketches the gesture-topic gossip
  provider against this contract, including the one extension it will
  need (topic-scoped trust) and why nothing else changes.

## Deviations from the spec sketch

- The trait deals in `SignedAnnouncement` rather than bare
  `Announcement`: the spec says announcements are signed, so the wire
  type carries its signature and the subscriber can't forget to check.
- `Announcement.author` is an iroh `PublicKey` (ed25519, as specified);
  provider addresses are excluded from the signed payload (they're
  refreshable hints) while provider identities are covered.
- Signature bytes travel as a length-checked `Vec<u8>` because serde
  cannot derive for `[u8; 64]`.