Show total building block cost in multi-selection panel

Implement the REQ-UI-MULTI-SELECTION addition: the selected building
panel now shows the total placement cost of a multi-selection, counting
only player-placeable buildings (HQ and defence stations excluded).
Construction sites are charged their type's full cost.

Add a shared BuildingsConfig::findBuildingDef accessor and reuse it in
BlueprintPanel to remove the duplicated by-type lookup loops.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DZR44tA8sn4dPqDzAVXyps

src/lib/config/BuildingsConfig.h

@@ -31,4 +31,18 @@ struct BuildingDef
 struct BuildingsConfig
 {
     std::vector<BuildingDef> buildings;
+
+    // Returns the definition for the given building type, or nullptr if the
+    // type has no entry in buildings.toml.
+    const BuildingDef* findBuildingDef(BuildingType type) const
+    {
+        for (const BuildingDef& def : buildings)
+        {
+            if (def.type == type)
+            {
+                return &def;
+            }
+        }
+        return nullptr;
+    }
 };

src/ui/BlueprintPanel.cpp

@@ -157,14 +157,8 @@ Blueprint BlueprintPanel::createBlueprintFromSelection() const
     {
         const Building* b = m_sim->buildings().findBuilding(id);
         if (!b) { continue; }
-        const bool placeable = [&]() {
+        const BuildingDef* def = m_config->buildings.findBuildingDef(b->type);
-            for (const BuildingDef& def : m_config->buildings.buildings)
+        if (def && def->playerPlaceable) { entries.push_back({ b }); }
-            {
-                if (def.type == b->type) { return def.playerPlaceable; }
-            }
-            return false;
-        }();
-        if (placeable) { entries.push_back({ b }); }
     }
 
     if (entries.empty()) { return Blueprint{}; }
@@ -213,14 +207,8 @@ int BlueprintPanel::computeBlueprintCost(const Blueprint& bp) const
     int total = 0;
     for (const BlueprintBuilding& bb : bp.buildings)
     {
-        for (const BuildingDef& def : m_config->buildings.buildings)
+        const BuildingDef* def = m_config->buildings.findBuildingDef(bb.type);
-        {
+        if (def) { total += def->cost; }
-            if (def.type == bb.type)
-            {
-                total += def.cost;
-                break;
-            }
-        }
     }
     return total;
 }

src/ui/SelectedBuildingPanel.cpp

@@ -694,6 +694,7 @@ void SelectedBuildingPanel::buildMulti(const std::vector<BuildingId>& ids)
     }
 
     bool hasBelt = false;
+    int totalCost = 0;
     QString text;
     for (const std::pair<const BuildingType, int>& entry : counts)
     {
@@ -703,7 +704,15 @@ void SelectedBuildingPanel::buildMulti(const std::vector<BuildingId>& ids)
         {
             hasBelt = true;
         }
+        // Total placement cost counts only player-placeable buildings; the HQ
+        // and defence stations are excluded (REQ-UI-MULTI-SELECTION).
+        const BuildingDef* def = m_config->buildings.findBuildingDef(entry.first);
+        if (def && def->playerPlaceable)
+        {
+            totalCost += def->cost * entry.second;
         }
+    }
+    text += tr("Total: %1 Building Blocks").arg(totalCost);
     m_titleLabel->setText(text.trimmed());
     m_titleLabel->show();