place the selection panel beside what it describes

src/ui/GameWorldView.h

@@ -226,6 +226,15 @@ private:
     // which is the only case that goes on to start a box drag.
     bool                     selectAtPoint(QPoint tile, QVector2D worldPos, bool additive);
     void                     selectInBox(bool additive);
+    // Publishes where on the screen the selection about to be made sits, so the
+    // selection panel can be placed beside it (REQ-UI-SELECTION-PANEL). Called with
+    // what is about to be selected, immediately before selecting it, and publishes
+    // nothing unless that selection is starting rather than growing.
+    void                     publishSelectionAnchor(
+                                 SelectionMode mode,
+                                 const std::vector<BuildingId>& buildings,
+                                 const std::vector<entt::entity>& actors,
+                                 const std::vector<entt::entity>& debris);
     void                     stepSpeed(int delta);
     void                     placeAtTile(QPoint tile);