implement copy building settings with shift + click gesture

src/lib/sim/BuildingConfig.h

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "BuildingId.h"
+#include "BuildingType.h"
+#include "ItemType.h"
+#include "ShipLayout.h"
+
+class Simulation;
+
+// The user-configurable settings of a single building or construction site: the
+// selected recipe / ship schematic, the shipyard module layout, and (for
+// splitters) the two output filters. Shared by the copy-settings gesture
+// (REQ-BLD-COPY-CONFIG) and blueprint capture (REQ-UI-BLUEPRINT-STORAGE).
+struct BuildingConfig
+{
+    BuildingType type = BuildingType::Miner;
+
+    // Selected recipe (Miner / Assembler) or ship schematic id (Shipyard); unset
+    // when nothing is selected.
+    std::optional<std::string> recipeId;
+
+    // Shipyard module layout (REQ-MOD-LAYOUT).
+    std::optional<ShipLayoutConfig> shipLayout;
+
+    // Splitter output filters (empty = accept all). isSplitter distinguishes an
+    // empty-filter splitter (a valid accept-all configuration) from a building
+    // type that has no splitter filters at all.
+    bool                  isSplitter = false;
+    std::vector<ItemType> splitterFilterA;
+    std::vector<ItemType> splitterFilterB;
+};
+
+// Reads the current configuration of the building or construction site identified
+// by id, handling operational buildings and sites alike. Returns std::nullopt if
+// no such building or site exists.
+std::optional<BuildingConfig> readBuildingConfig(const Simulation& sim, BuildingId id);