chore: Новый черновик DRAFT, удалить старые docs-v

examples/demo-backend/docs/WEBSOCKET.md

@@ -0,0 +1,79 @@
+# Socket.IO chat contract
+
+## Connection
+
+Connect to the Complex API namespace:
+
+```text
+http://localhost:3002/chat
+```
+
+The browser must already have a valid `demo_session` cookie and use credentials. Both `websocket` and `polling` transports are enabled.
+
+```ts
+import { io } from "socket.io-client";
+
+const socket = io("http://localhost:3002/chat", {
+  withCredentials: true,
+});
+```
+
+An invalid session receives `chat:error` and is disconnected.
+
+## Client events
+
+### `chat:join`
+
+```json
+{
+  "organizationId": "org-acme",
+  "conversationId": "conversation-support"
+}
+```
+
+Response event: `chat:joined`.
+
+### `chat:leave`
+
+Uses the same payload. Response event: `chat:left`.
+
+### `message:send`
+
+```json
+{
+  "organizationId": "org-acme",
+  "conversationId": "conversation-support",
+  "text": "Can you check this order?",
+  "clientMessageId": "frontend-generated-uuid"
+}
+```
+
+Response event: `message:ack`. Room broadcast: `message:created`.
+
+Sending the same `clientMessageId` again returns the existing message. Frontends should also deduplicate incoming `message:created` by server message `id`.
+
+### `typing:start` and `typing:stop`
+
+Use the `chat:join` payload. Other room members receive `typing:started` or `typing:stopped`:
+
+```json
+{
+  "conversationId": "conversation-support",
+  "userId": "complex-user-support"
+}
+```
+
+## Error event
+
+`chat:error` always contains a stable shape:
+
+```json
+{
+  "code": "CHAT_OPERATION_FAILED",
+  "message": "Conversation not found."
+}
+```
+
+## Reconnect expectations
+
+After reconnect, the frontend should join active conversations again and reload messages after its last known cursor. A session expired by `POST /api/v1/testing/session/expire` rejects the next Socket.IO connection.