add contact convention

Author: uriva

conventions/contact.md

@@ -0,0 +1,27 @@
+# Contact Convention
+
+Contacts are regular encrypted documents with this JSON shape:
+
+```json
+{
+  "kind": "contact",
+  "title": "Jane Doe",
+  "content": "Personal assistant instructions: prefer email for non-urgent tasks.",
+  "contactDetails": {
+    "name": "Jane Doe",
+    "email": "jane@example.com",
+    "phone": "1234567890",
+    "slack": "U12345",
+    "teams": "user@domain.com",
+    "telegram": "@janedoe",
+    "aliceAndBotPublicSignKey": "alice-and-bot-public-key"
+  }
+}
+```
+
+Rules:
+
+- `kind` MUST be `"contact"`.
+- `title` is the contact's name or display name.
+- `content` can contain freeform markdown notes about the contact.
+- `contactDetails` holds the structured contact fields previously handled by the DB.