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/StreamHub.h

@@ -231,11 +231,27 @@ private:
      * @return true if the session was started.
      */
     bool AddSourceInternal(const char *label, const char *addrPort,
-                           const char *mcGroup, uint16 dataPort);
+                           const char *mcGroup, uint16 dataPort,
+                           const char *transport = "udp",
+                           const char *streamName = "");
+
+    /**
+     * @brief TCP source whose streamName is a comma separated list "a,b,c": one
+     * TCPSClient (one socket) feeds one session per stream, labelled
+     * "<label>_<stream>" (just "<stream>" without a label). Session ids are
+     * "s<N>", or "<idPrefix>_<stream>" when @p idPrefix (the config node id) is given.
+     * @return true if every session was started (none is left behind otherwise).
+     */
+    bool AddMuxSourceInternal(const char *label, const char *host, uint32 port,
+                              const char *addrPort, const char *streamList,
+                              const char *idPrefix = static_cast<const char *>(0));
+
+    /** @brief Detach @p slot from its shared receiver; frees the receiver with its last session. */
+    void ReleaseMuxSlot(uint32 slot);
 
     /**
      * @brief Load sources and calibration from sourcesFile_ (a flat JSON array
-     * of {"label","addr","multicastGroup","dataPort"} source blocks and
+     * of {"label","addr","multicastGroup","dataPort","transport","streamName"} source blocks and
      * {"source","signal","scale","offset","unit"} calibration blocks).
      * @param skipActive when true, a source whose "host:port" is already
      * streaming is left alone instead of being started a second time.
@@ -247,7 +263,7 @@ private:
     bool LoadSourcesFile(bool skipActive, bool clearCalibration = false);
 
     /** @return true if a session for this "host:port" is already active. */
-    bool SourceIsActive(const char *addrPort);
+    bool SourceIsActive(const char *addrPort, const char *streamName = "");
 
     /**
      * @brief Store or replace one calibration entry.  An identity entry
@@ -280,6 +296,21 @@ private:
 
     /* ---- Members --------------------------------------------------------- */
 
+    /** A multiplexed receiver shared by several sessions (deleted with the last one). */
+    struct MuxClient {
+        MuxClient() : client(static_cast<MARTe::TCPSClient *>(0)), refs(0u) {}
+        ~MuxClient() { delete client; }
+        MARTe::TCPSClient *client;
+        uint32             refs;
+    private:
+        MuxClient(const MuxClient &);
+        MuxClient &operator=(const MuxClient &);
+    };
+    /* Declared before sessions_ so it is destroyed after them: a session stops
+     * its (facade of a) shared receiver from its own destructor. */
+    MuxClient         muxClients_[kMaxSessions];
+    MARTe::int32      sessionMux_[kMaxSessions]; ///< Index into muxClients_, or -1
+
     UDPSourceSession  sessions_[kMaxSessions];
     uint32            numSessions_;       ///< Count of active sessions (not an upper slot bound)
     bool              sessionActive_[kMaxSessions]; ///< Per-slot in-use flag (slots are not compacted on removal)