fix: reset msgSerial on reconnect after suspension

- Ensure `msgSerial` is reset to `0` when reconnecting from the suspended state.
- Added a unit test to verify this behavior.

Author: ttypic

lib/src/main/java/io/ably/lib/transport/ConnectionManager.java

@@ -1285,6 +1285,8 @@ private synchronized void onConnected(ProtocolMessage message) {
                 addPendingMessagesToQueuedMessages(true);
                 channels.transferToChannelQueue(extractConnectionQueuePresenceMessages());
             }
+        } else {
+            msgSerial = 0;
         }
 
         connection.id = message.connectionId;

lib/src/test/java/io/ably/lib/test/realtime/RealtimeConnectFailTest.java

@@ -139,6 +139,24 @@ public void connect_fail_suspended() {
         }
     }
 
+    @Test
+    public void connect_after_suspend_should_clean_msg_serial() throws AblyException {
+        ClientOptions opts = createOptions(testVars.keys[0].keyStr);
+        opts.disconnectedRetryTimeout = Integer.MAX_VALUE;
+        opts.suspendedRetryTimeout = Integer.MAX_VALUE;
+        try (AblyRealtime ably = new AblyRealtime(opts)) {
+            ConnectionWaiter waiter = new ConnectionWaiter(ably.connection);
+            waiter.waitFor(ConnectionState.connecting);
+            ably.connection.connectionManager.requestState(ConnectionState.suspended);
+            waiter.waitFor(ConnectionState.suspended);
+            ably.connection.connectionManager.msgSerial = 100;
+            assertEquals("Verify suspended state reached", ConnectionState.suspended, ably.connection.state);
+            ably.connect();
+            waiter.waitFor(ConnectionState.connected);
+            assertEquals(0, ably.connection.connectionManager.msgSerial);
+        }
+    }
+
     /**
      * Verify that the connection in the disconnected state (after attempts to
      * connect to a non-existent ws host) allows an immediate explicit connect