fix(ibm): initialize the burning-surface fields on particle-cloud IB patches

particle_cloud_ibs is allocated without default initialization, and s_add_cloud_particle set only the geometry/motion members. s_reduce_ib_patch_array then copies the whole struct into patch_ib, overwriting the zeroed defaults from s_assign_default_values_to_user_inputs -- so v_blow, inj_species and burn_rate_exp/pref reached the solver as uninitialized memory.

That was latent until this branch added the first read of those members in m_ibm: a garbage v_blow > 0 superimposes a garbage wall-normal velocity on the ghost points, which NaNs the field. It reproduced only where the allocation is not already zero-filled -- Frontier AMD failed 2D_mibm_particle_cloud with 'ICFL is NaN' at step 2 while every NVHPC lane (and local CPU/OMP/ACC) passed. Sets the four fields for the inert particle surfaces; audited that these are exactly the patch_ib members m_ibm reads (airfoil_id/model_id/length_x remain unset but are never read for circle/sphere particles).

Author: sbryngelson

src/simulation/m_particle_cloud.fpp

@@ -300,6 +300,17 @@ contains
         particle_cloud_ibs(ib_idx)%moving_ibm = particle_cloud(cloud_idx)%moving_ibm
         particle_cloud_ibs(ib_idx)%slip = .false.
 
+        ! Particles are inert surfaces. These must be set explicitly: particle_cloud_ibs is
+        ! allocated (not default-initialized) and s_reduce_ib_patch_array copies the whole
+        ! struct into patch_ib, overwriting the defaults from
+        ! s_assign_default_values_to_user_inputs -- so anything left unset here reaches the
+        ! solver as uninitialized memory (a nonzero v_blow injects a garbage wall-normal
+        ! velocity and NaNs the field).
+        particle_cloud_ibs(ib_idx)%v_blow = 0._wp
+        particle_cloud_ibs(ib_idx)%inj_species = 0
+        particle_cloud_ibs(ib_idx)%burn_rate_exp = 0._wp
+        particle_cloud_ibs(ib_idx)%burn_rate_pref = 0._wp
+
     end subroutine s_add_cloud_particle
 
     !> Xorshift PRNG. Advances seed in-place and returns a value in [0, 1).