Update channel CPU shim include and retain frozen projected driver

tests/unit/cpp/channel_root.cpp

@@ -42,6 +42,7 @@ inline float __fdiv_rn(float a,float b){return a/b;}
 #include "step/one_step_double.cu"
 #else
 #include "core/cell_kind.cuh"
+#include "operators/block_collision.cuh"
 #include "step/block_channel.cu"
 #endif
 int main(){

tests/validation/multigrid/check_projected_pairs.py

@@ -269,7 +269,7 @@ def remap_case(ctx, shifted, raw):
             refinements=refs[:2],level_blocks=blocks[:3],explosion='projected_linear') as run:
         initialize(run); run.step(1)
         before = snapshot(run,raw)
-        with run.remap_finest([(22,22,42,42),(72,68,76,76)]) as clone:
+        with run.remap_child([(22,22,42,42),(72,68,76,76)]) as clone:
             if clone._explosion != 'projected_linear' or any(p.neighbors is None for p in clone._pairs):
                 raise AssertionError('remap lost projected selection')
             if clone.step_count != 1: raise AssertionError('remap lost synchronized count')