float the build buttons as a horizontal bar over the game world and show key bindings inside build buttons

src/ui/InputMapper.h

@@ -1,5 +1,8 @@
 #pragma once
 
+#include <QString>
+
+#include "BuildingType.h"
 #include "WorldCamera.h"
 
 class QKeyEvent;
@@ -24,6 +27,12 @@ class QKeyEvent;
 class InputMapper
 {
 public:
+    // The build hotkey that selects the given building type, spelled for display on
+    // its build button's badge (REQ-UI-BUILD-COST): "1" for a plain digit, "⇧1" for
+    // a Shift+digit, and an empty string for a building type with no build hotkey.
+    // Lives here so the badge and the key handling read the same binding table.
+    static QString getBuildHotkeyLabel(BuildingType type);
+
     // Both return true when the key was consumed; the caller passes anything else
     // on to its base class so unrelated shortcuts keep working.
     bool handleKeyPress(QKeyEvent* event);