Rename replay → initChannelState

Rename the query parameter, function, and all related comments
from 'replay' to 'initChannelState' to better reflect the
semantics: the server initializes channel state for the
reconnecting client rather than replaying past events.

README.md

@@ -1036,7 +1036,7 @@ Return the current user's session state.
 
 | 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. |
+| `initChannelState` | 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
@@ -1070,9 +1070,9 @@ curl -s http://localhost:8080/api/v1/state \
   -H "Authorization: Bearer $TOKEN" | jq .
 ```
 
-**Reconnect with channel replay:**
+**Reconnect with channel state initialization:**
 ```bash
-curl -s "http://localhost:8080/api/v1/state?replay=1" \
+curl -s "http://localhost:8080/api/v1/state?initChannelState=1" \
   -H "Authorization: Bearer $TOKEN" | jq .
 ```