make recipe selection and buffers of smelter and reprocessing plant behave like other buildings, except that a recipe may be chosen automatically

src/ui/RecipeSelectionDialog.cpp

@@ -50,7 +50,13 @@ std::vector<RecipeSelectionOption> buildRecipeSelectionOptions(
     BuildingType type, Simulation& sim, const GameConfig& config)
 {
     std::vector<RecipeSelectionOption> options;
-    options.push_back({std::string(), QObject::tr("(None)"), RecipeLineRow::Spec()});
+    // The clearing option. On a building that picks its own recipe it does not leave the
+    // building idle but hands it back to that selection, and says so
+    // (REQ-UI-SELECT-OPTIONS, REQ-BLD-AUTO-RECIPE).
+    options.push_back({std::string(),
+                       isAutoRecipeBuildingType(type) ? QObject::tr("(Auto)")
+                                                      : QObject::tr("(None)"),
+                       RecipeLineRow::Spec()});
 
     if (type == BuildingType::Shipyard)
     {