split the selection panel into one card per kind of selection

src/ui/selection/BuildingTarget.cpp

@@ -0,0 +1,34 @@
+#include "BuildingTarget.h"
+
+#include "FactoryQueries.h"
+#include "SelectionContext.h"
+#include "Simulation.h"
+
+BuildingTarget resolveBuildingTarget(const SelectionContext& context, BuildingId id)
+{
+    BuildingTarget target;
+    target.building = findBuilding(context.sim->getFactoryState(), id);
+    target.site     = target.building
+        ? nullptr
+        : findSite(context.sim->getFactoryState(), id);
+    if (!target.isValid())
+    {
+        return target;
+    }
+
+    target.type       = target.building ? target.building->type       : target.site->type;
+    target.recipeId   = target.building ? target.building->recipeId   : target.site->recipeId;
+    target.shipLayout = target.building ? target.building->shipLayout : target.site->shipLayout;
+    target.anchor     = target.building ? target.building->anchor     : target.site->anchor;
+    return target;
+}
+
+std::optional<BuildingId> asConstructionSite(const SelectionContext& context,
+                                             BuildingId id)
+{
+    if (findSite(context.sim->getFactoryState(), id) != nullptr)
+    {
+        return id;
+    }
+    return std::nullopt;
+}