split the selection panel into one card per kind of selection

src/ui/selection/BufferedBuildingContent.h

@@ -0,0 +1,53 @@
+#pragma once
+
+#include <map>
+#include <string>
+
+#include "BuildingId.h"
+#include "SelectionContent.h"
+
+struct Building;
+class BufferSection;
+class ProductionSection;
+
+// Shared body of the four cards that show one building with buffers -- the Miner and
+// Assembler, the Smelter and Reprocessing Plant, the Shipyard, and the Salvage Bay
+// (REQ-UI-SELECTION-CONTENT). All four show the same header status, buffer contents and
+// production progress; they differ only in what one production cycle costs and how long
+// it takes, which is what the subclass supplies.
+//
+// This is implementation sharing, not a catalog entry: every concrete subclass is one
+// row of the content catalog.
+class BufferedBuildingContent : public SelectionContent
+{
+    Q_OBJECT
+
+protected:
+    // What one production cycle of this building consumes, produces, and takes.
+    struct CycleInfo
+    {
+        std::map<std::string, int> perCycleInputs;
+        std::map<std::string, int> perCycleOutputs;
+        // False when the building produces nothing at all (the Salvage Bay,
+        // REQ-BLD-SALVAGE-BAY) or has no recipe or schematic selected yet: the
+        // production section is then not shown (REQ-UI-PRODUCTION-PROGRESS).
+        bool runsProduction = false;
+        // 0 while an auto-recipe building sits between cycles, when no single recipe
+        // names a cycle time; the progress line then reads "idle".
+        double durationSeconds = 0.0;
+    };
+
+    BufferedBuildingContent(const SelectionContext& context, BuildingId id,
+                            QWidget* parent);
+
+    virtual CycleInfo getCycleInfo(const Building& building) const = 0;
+
+    BuildingId getBuildingId() const { return m_id; }
+
+    void refreshRuntime() override;
+
+private:
+    BuildingId         m_id;
+    BufferSection*     m_buffers;
+    ProductionSection* m_production;
+};