Add DM privacy and signing adapter documentation

docs/nostr-event-schemas.md

@@ -79,6 +79,9 @@ sign/encrypt calls. Call `clearActiveSigner()` on logout if your integration
 manages session state manually; the built-in logout handler already does this
 for the default extension flow.
 
+For adapter implementation details and test guidance, see
+[`docs/signing-adapter.md`](signing-adapter.md).
+
 ### Accessing raw events
 
 `NostrClient` now keeps a lightweight cache of parsed videos alongside a
@@ -189,6 +192,10 @@ bitvid now consumes both legacy direct messages (kind `4`) and modern gift-wrap
 
 The `isPrivate` flag in Content Schema v3 marks cards that should stay off shared or public grids. Clients should suppress these events for everyone except the owner, even though the payload stays in clear text for compatibility.
 
+For the privacy model, relay hint selection flow, and user controls (privacy
+toggle, relay list publishing, and metadata toggles), see
+[`docs/dm-privacy-model.md`](dm-privacy-model.md).
+
 If you introduce a new Nostr feature, add its schema to
 `js/nostrEventSchemas.js` so that the catalogue stays complete and so existing
 builders inherit the same debugging knobs.