Add PLY export when infer_gs is enabled

The export_to_gs_ply function was never being called - only export_to_gs_video.
Now PLY files are exported alongside videos for download.

depth_anything_3/app/modules/model_inference.py

@@ -205,7 +205,7 @@ class ModelInference:
             num_max_points=int(num_max_points),
         )
 
-        # export to gs video if needed
+        # export to gs video and ply if needed
         if infer_gs:
             mode_mapping = {"extend": "extend", "smooth": "interpolate_smooth"}
             print(f"GS mode: {gs_trj_mode}; Backend mode: {mode_mapping[gs_trj_mode]}")
@@ -218,6 +218,11 @@ class ModelInference:
                 vis_depth="hcat",
                 video_quality=gs_video_quality,
             )
+            # Export PLY file for download/interactive viewing
+            from depth_anything_3.utils.export.gs import export_to_gs_ply
+            print("Exporting Gaussian Splat PLY file...")
+            export_to_gs_ply(prediction, export_dir=target_dir)
+            print(f"PLY exported to {target_dir}/gs_ply/")
 
         # Save predictions.npz for caching metric depth data
         self._save_predictions_cache(target_dir, prediction)