fix: PacketStreamFilter socket leak on abrupt disconnect

This fix prevents TCP sockets from accumulating in CLOSE_WAIT following a
network interruption.

StreamInputShutdown ignored events that occurred while waiting for parts of a
partially received packet.
This could prevent the higher-level state machine from receiving the disconnect
signal and closing the socket.

The filter now correctly treats a stream closure during mid-packet reception as
a protocol error, ensuring the disconnect event is propagated, and proceeds with
the shutdown.

src/lib/deskflow/PacketStreamFilter.cpp

@@ -164,8 +164,17 @@ void PacketStreamFilter::filterEvent(const Event &event)
     std::scoped_lock lock{m_mutex};
     m_inputShutdown = true;
     if (m_size != 0) {
+      if (m_buffer.getSize() >= m_size) {
+        // we have a complete packet, so we can process it before
+        // shutting down.
         return;
       }
+      // we have a partial packet, but the stream has shut down.
+      // we'll never get the rest of the packet, so we should
+      // signal an error and then shut down.
+      m_events->addEvent(Event(EventTypes::StreamInputFormatError, getEventTarget()));
+      m_size = 0;
+    }
   }
 
   // pass event