Add gateway realtime fanout and cursor pagination docs

README.md

@@ -11,6 +11,7 @@ Each user has a **home server** where their identity lives (keypair), and can se
 - **Client does everything** - syncs, cross-server requests, profile updates
 
 See [ARCHITECTURE.md](./ARCHITECTURE.md) for full details.
+See [CLIENT_INTEGRATION.md](./CLIENT_INTEGRATION.md) for client protocol/API integration details.
 
 ## Quick Start