docs: document ?replay=1 query parameter for GET /state

README.md

@@ -937,6 +937,12 @@ Return the current user's session state.
 
 **Request:** No body. Requires auth.
 
+**Query Parameters:**
+
+| Parameter | Type   | Default | Description |
+|-----------|--------|---------|-------------|
+| `replay`  | string | (none)  | When set to `1`, enqueues synthetic JOIN + TOPIC + NAMES messages for every channel the session belongs to into the calling client's queue. Used by the SPA on reconnect to restore channel tabs without re-sending JOIN commands. |
+
 **Response:** `200 OK`
 ```json
 {
@@ -969,6 +975,12 @@ curl -s http://localhost:8080/api/v1/state \
   -H "Authorization: Bearer $TOKEN" | jq .
 ```
 
+**Reconnect with channel replay:**
+```bash
+curl -s "http://localhost:8080/api/v1/state?replay=1" \
+  -H "Authorization: Bearer $TOKEN" | jq .
+```
+
 ### GET /api/v1/messages — Poll Messages (Long-Poll)
 
 Retrieve messages from the client's delivery queue. This is the primary