Restore UseDevice for submesh vectors to fix GPU operator-vector mismatch

Author: dnpham23

palace/models/surfacecurlsolver.cpp

@@ -308,11 +308,12 @@ void SolveSurfaceCurlProblem(const SurfaceFluxData &flux_data, const IoData &iod
   }
 
   // Compute boundary-interior coupling before applying boundary conditions.
-  // Keep vectors on host: the submesh solver uses host-side operations (direct indexing,
-  // GroupCommunicator reductions) that are incompatible with device memory.
   Vector RHS(submesh_nd_fespaces.GetFinestFESpace().GetTrueVSize());
   Vector X(submesh_nd_fespaces.GetFinestFESpace().GetTrueVSize());
   Vector boundary_vals(submesh_nd_fespaces.GetFinestFESpace().GetTrueVSize());
+  RHS.UseDevice(true);
+  X.UseDevice(true);
+  boundary_vals.UseDevice(true);
 
   // Get boundary values directly from MFEM GridFunction
   A.GetTrueDofs(boundary_vals);