feat(editor): import ADT doodad/WMO placements on load

- Loading an existing ADT now imports its MDDF (doodad) and MODF (WMO)
  placements into the object placer with correct position/rotation/scale
- Allows editing zones that already have objects placed in them
- Mutable getObjects() accessor for bulk import operations
- Log shows imported doodad + WMO count on load

tools/editor/object_placer.hpp

@@ -54,6 +54,7 @@ public:
     bool loadFromFile(const std::string& path);
 
     const std::vector<PlacedObject>& getObjects() const { return objects_; }
+    std::vector<PlacedObject>& getObjects() { return objects_; }
     void clearAll() { objects_.clear(); undoStack_.clear(); selectedIdx_ = -1; }
     size_t objectCount() const { return objects_.size(); }