fix(editor): add M2 render diagnostics to Info panel for NPC debugging

- Info panel now shows M2 renderer stats: model count, instance count,
  draw call count — visible in real-time to diagnose NPC rendering issues
- When placing NPCs: if models=0/instances=0, the model failed to load
  If models>0 but draws=0, it's a culling/frame-sync issue
  If draws>0, the model IS rendering but may be too small to see

tools/editor/editor_viewport.hpp

@@ -61,6 +61,7 @@ public:
     glm::vec3 getLightDir() const { return lightDir_; }
 
     rendering::TerrainRenderer* getTerrainRenderer() { return terrainRenderer_.get(); }
+    rendering::M2Renderer* getM2Renderer() { return m2Renderer_.get(); }
 
 private:
     bool createPerFrameResources();