In the two Step() functions that handle both Patch and Shell Patch,
defer the Patch error check until after Shell Patch computation completes,
then perform a single combined MPI_Allreduce instead of two separate ones.
This eliminates 4 MPI_Allreduce calls per timestep (2 per Step function,
Predictor + Corrector phases each). The optimization is mathematically
equivalent: in normal execution (no NaN) behavior is identical; on error,
both Patch and Shell data are dumped before MPI_Abort.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
