feat(tcp): TCPStreamer DataSources, in-process TCPStreamService, stream multiplexing and TCPStreamJoin

Add TCPStreamer/TCPStreamerClient (TCP transport behind the UDPSServerI/UDPSClientI
seam), an optional single in-process TCPStreamService serving many streams over
worker threads, multiplexed SUBSCRIBE (comma list, stream index in fragmentIdx),
and TCPStreamJoin, which merges several streams into one sample-and-hold stream
paced by a master. StreamHub takes a comma list of streams over one connection.
Includes GTests, E2E scenarios s58-s73 and docs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Source/Applications/StreamHub/UDPSourceSession.h

@@ -11,6 +11,7 @@
 #define STREAMHUB_UDP_SOURCE_SESSION_H_
 
 #include "UDPSClient.h"
+#include "TCPSClient.h"
 #include "UDPSProtocol.h"
 #include "FastPollingMutexSem.h"
 #include "HighResolutionTimer.h"
@@ -158,11 +159,23 @@ public:
      * @param maxPts    Ring buffer capacity per signal.
      * @param mcGroup   Multicast group (empty string = unicast).
      * @param dataPort  Multicast data port (0 = port+1).
+     * @param transport "udp" (default) or "tcp". TCP ignores mcGroup/dataPort.
+     * @param streamName TCP only: stream to subscribe to on a TCPStreamService
+     *                   ("" = plain TCPStreamer, no subscription).
+     * @param external  Optional receiver owned by the caller (one stream of a
+     *                  multiplexed TCPSClient, see TCPSClient::GetStream()). When set the
+     *                  session does not create or configure its own client; call
+     *                  DetachClient() before the receiver is destroyed.
      * @return true on success.
      */
     bool Initialise(const char *id, const char *label,
                     const char *addr, uint16 port, uint32 maxPts,
-                    const char *mcGroup = "", uint16 dataPort = 0u);
+                    const char *mcGroup = "", uint16 dataPort = 0u,
+                    const char *transport = "udp", const char *streamName = "",
+                    MARTe::UDPSClientI *external = static_cast<MARTe::UDPSClientI *>(0));
+
+    /** @brief Stop and forget an external receiver (no-op for built-in receivers). */
+    void DetachClient();
 
     /** @brief Start the UDPSClient background thread. */
     bool Start();
@@ -236,6 +249,12 @@ public:
     /** @return Multicast data port (0 = port+1 default). */
     uint16 GetDataPort() const;
 
+    /** @return "udp" or "tcp". */
+    StreamString GetTransport() const;
+
+    /** @return TCP stream name ("" = none). */
+    StreamString GetStreamName() const;
+
     /** @return true after the first CONFIG packet has been fully parsed. */
     bool IsConfigured() const;
 
@@ -443,13 +462,18 @@ private:
     uint16       port_;
     StreamString mcGroup_;   ///< Multicast group ("" = unicast)
     uint16       dataPort_;  ///< Multicast data port (0 = port+1)
+    StreamString transport_; ///< "udp" or "tcp"
+    StreamString streamName_;///< TCPStreamService stream name ("" = none)
     uint32       maxPoints_;
     uint32       ringTemporal_;  ///< Ring capacity for multi-element signals
     uint32       ringScalar_;    ///< Ring capacity for scalar signals
     bool         initialised_;
 
-    /* UDPSClient (owns the background thread) */
-    UDPSClient   client_;
+    /* Receivers (each owns a background thread); client_ points at the active one. */
+    UDPSClient   udpClient_;
+    MARTe::TCPSClient tcpClient_;
+    MARTe::UDPSClientI *client_;
+    bool                external_;   ///< client_ is owned by the caller
 
     /* Signal metadata — protected by metaMutex_ */
     mutable FastPollingMutexSem metaMutex_;