livoxProto1: export getReturnModeReq; cache result in Device

commonLibs/livoxProto1/device.h

@@ -103,6 +103,14 @@ private:
 	class GetReturnModeReq;
 
 public:
+	enum class ReturnMode : uint8_t
+	{
+		SingleFirst		= 0x00,
+		SingleStrongest	= 0x01,
+		Dual			= 0x02,
+		Triple			= 0x03
+	};
+
 	// Utility methods
 	std::optional<std::string> getSmoIp(const std::string& deviceIP);
 
@@ -158,6 +166,9 @@ public:
 	std::unique_ptr<boost::asio::posix::stream_descriptor> pcloudDataSocketDesc;
 	std::atomic<bool> pcloudDataActive;
 
+	// Cached last-known return mode for this device
+	ReturnMode currentReturnMode = ReturnMode::SingleFirst;
+
 public:
 	// UDP datagram handling
 	void handleUdpDgram(