feat: WOB→WMO conversion and loading in client terrain manager

- WoweeBuildingLoader::toWMOModel() converts WOB groups to WMOModel
  with vertices, indices, normals, texCoords, and vertex colors
- TerrainManager now loads WOB files from custom_zones/buildings/
  and converts to WMOModel for the WMO renderer pipeline
- WMOGroup indices converted from uint32 to uint16 for renderer compat

Client open format support — 4 of 6 now loading:
- FULL: WOT/WHM terrain, PNG textures, WOM models
- LOAD: WOB buildings (converts to WMOModel, render pipeline TODO)
- DETECT: zone.json (scanned), JSON DBC (scanned)

include/pipeline/wowee_building.hpp

@@ -53,6 +53,9 @@ public:
     static WoweeBuilding load(const std::string& basePath);
     static bool save(const WoweeBuilding& building, const std::string& basePath);
     static bool exists(const std::string& basePath);
+
+    // Convert WOB to WMOModel for the client's WMO renderer
+    static bool toWMOModel(const WoweeBuilding& building, class WMOModel& outModel);
 };
 
 } // namespace pipeline