fix(pibasetransfer): make shared flags std::atomic<bool> to eliminate data race

Flags break_, is_sending, is_receiving, is_pause are accessed from
both the send thread (send_process) and the read thread (received)
without synchronization. Plain bool reads/writes from multiple threads
is undefined behavior per C++ standard. Convert to std::atomic<bool>
with proper initializers.

libs/main/io_utils/pibasetransfer.h

@@ -28,6 +28,8 @@
 #include "picrc.h"
 #include "pidiagnostics.h"
 
+#include <atomic>
+
 
 //! \~\ingroup IO-Utils
 //! \~\brief
@@ -301,7 +303,7 @@ protected:
 	bool send_process();
 
 	uint packet_header_size, part_header_size;
-	bool break_, is_sending, is_receiving, is_pause;
+	std::atomic<bool> break_{true}, is_sending{false}, is_receiving{false}, is_pause{false};
 	PIString state_string;
 	llong bytes_all, bytes_cur;