feat(editor): open terrain format integrated into export workflow

- File > Export Open Format (.wot/.whm) menu item for standalone export
- Every zone export (Ctrl+S, Export Zone) now also writes .wot/.whm
  alongside the ADT/WDT — dual format output
- Export package now contains: ADT + WDT + WOT + WHM + JSON files
- Both Blizzard-compatible (for existing servers) and open format
  (for wowee-native loading and redistribution)

tools/editor/editor_app.hpp

@@ -37,6 +37,7 @@ public:
     void exportZone(const std::string& outputDir);
     void quickSave();
     void exportContentPack(const std::string& destPath);
+    void exportOpenFormat(const std::string& basePath);
 
     void requestQuit();
     void resetCamera();