fix(stability): cap history buffer on allocation failure instead of silently dropping data

When vector push_back fails due to heap fragmentation, cap maxSize to
current buffer size and switch to circular overwrite mode. Previously,
every subsequent addPoint call would also fail silently, stopping all
historical data recording permanently.

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

Author: cbrown350

lib/HistoricalDataManager/HistoricalDataManager.cpp

@@ -49,7 +49,12 @@ void HistoricalDataManager::addPoint(const DataPoint& point) {
         try {
             buffer.push_back(point);
         } catch (...) {
-            // Allocation failed — skip this data point rather than crash
+            // Allocation failed — cap maxSize so we switch to circular
+            // overwrite mode instead of silently dropping all future points
+            maxSize = buffer.size();
+            if (maxSize == 0) return;
+            buffer[currentIndex] = point;
+            currentIndex = (currentIndex + 1) % maxSize;
             return;
         }
     } else {