split the selection panel into one card per kind of selection

src/ui/selection/DebrisScrap.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <vector>
+
+#include "entt/entity/entity.hpp"
+
+class EntityAdmin;
+
+// Remaining scrap summed over the given debris, skipping pieces that have already been
+// collected or despawned (REQ-RES-DEBRIS-DROP). Shared by the debris card and the field
+// count summary, which show the same total in two shapes (REQ-UI-DEBRIS-PANEL,
+// REQ-UI-FIELD-MULTI-SELECTION).
+int sumDebrisScrap(const EntityAdmin& admin, const std::vector<entt::entity>& debris);