fix: three StreamHub C++ defects from final code review

Finding 1 (HandleReloadConfig data loss): move ClearCalibration inside
LoadSourcesFile so the table is wiped only after a successful fread.
Adds a clearCalibration bool parameter (default false); the reload path
passes true, the startup path passes false.

Finding 2 (JSON injection via unit/source/signal): add JsonEscape()
static helper (escapes \", \\, \n \r \t, and \u00XX for other control
chars). Applied at all three emission sites: BroadcastCalibration,
HandleSaveSources, and BroadcastSources (label). Teach JsonGetString to
unescape the same set on read, so values round-trip correctly.

Finding 3 (%.17g verbosity): add ShortFloat() static helper that tries
%.15g then %.16g then %.17g, stopping at the first precision whose
strtod() output compares equal to the original. Applied at both float
emission sites. 0.1 now prints as "0.1", not "0.10000000000000001".

Minor: fix two inaccurate comments in StreamHub.h — the CalibrationEntry
rationale (not a 133 MB / address-limit issue; the real reason is no
per-entry heap churn, STL-free, trivially copyable) and "chars" to "bytes"
for the unit cap.

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

Source/Applications/StreamHub/StreamHub.h

@@ -57,15 +57,15 @@ static const uint32 kMaxUnitLen = 16u;
  * add-order and would rebind if the source list were reordered) and by the
  * BASE signal name (no "[i]" suffix: one entry covers a whole array signal).
  *
- * Fixed-size char arrays are used deliberately: embedding 256 StreamString
- * (each of which allocates its own heap buffer) into a 133 MB struct that is
- * itself heap-allocated pushes offsets beyond the canonical x86-64 address
- * limit and causes a SIGSEGV in the constructor.
+ * Fixed-size char arrays are used deliberately: they avoid per-entry heap
+ * churn (no StreamString allocation per calibration slot), keep the type free
+ * of STL, and make a CalibrationEntry snapshot trivially copyable under the
+ * calibration mutex lock.
  */
 struct CalibrationEntry {
     char           source[128]; ///< Source label
     char           signal[128]; ///< Base signal name (no "[i]" suffix)
-    char           unit[17];    ///< Unit override (max kMaxUnitLen chars + NUL)
+    char           unit[17];    ///< Unit override (max kMaxUnitLen bytes + NUL)
     MARTe::float64 scale;
     MARTe::float64 offset;
 };
@@ -211,9 +211,12 @@ private:
      * {"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.
+     * @param clearCalibration when true, the calibration table is cleared
+     * after a successful fread (never before), so a transient I/O failure
+     * does not silently wipe user calibration data.
      * @return true if the file was read.
      */
-    bool LoadSourcesFile(bool skipActive);
+    bool LoadSourcesFile(bool skipActive, bool clearCalibration = false);
 
     /** @return true if a session for this "host:port" is already active. */
     bool SourceIsActive(const char *addrPort);