pre_process broadcasts the integer hcid patch member with the real datatype (mpi_p) #1579

Found by the post-merge broadcast audit of the #1550-#1556 series. patch_icpp(i)%hcid is integer (m_derived_types.fpp:307) but sits in pre_process's mpi_p patch-member broadcast loop (src/pre_process/m_mpi_proxy.fpp:94 on master) — an 8-byte real transfer over a 4-byte integer, the same UB class as the bc%beg/end fix in #1553. Consumed on all ranks (m_icpp_patches.fpp:210+). Practical severity low (works by adjacency; size-exact under --single), but it is a type-mismatched MPI operation. Introduced 2023-07-31 (3fdbddf2a, @wilfonba). Fix: move hcid to the MPI_INTEGER group.