keep an auto-recipe building's summary between its cycles

src/ui/selection/AutoProductionContent.h

@@ -1,12 +1,14 @@
 #pragma once
 
+#include <string>
+
 #include "BufferedBuildingContent.h"
 #include "SelectionContentFactory.h"
 
 // The card for a Smelter or a Reprocessing Plant (REQ-UI-SELECTION-CONTENT). Both
 // auto-process whatever they receive and have no player-facing recipe selection
 // (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING), so the card has no configuration group at
-// all; its cycle is whichever recipe is currently in production.
+// all; its cycle is whichever recipe is in production, or the last one that was.
 class AutoProductionContent : public BufferedBuildingContent
 {
     Q_OBJECT
@@ -17,4 +19,11 @@ public:
 
 protected:
     CycleInfo getCycleInfo(const BuildingTarget& target) const override;
+
+private:
+    // The recipe last seen in production, which keeps describing the cycle while the
+    // building sits between cycles (REQ-UI-RECIPE-SUMMARY). Mutable because it is a
+    // record of what getCycleInfo() has observed rather than state of its own: the card
+    // shows the same thing whether or not it has been asked before.
+    mutable std::string m_lastRecipeId;
 };