test_runtime_child_remap: inject remap body rejects through the boundary record

The removed _boundaries list made the two body-reject patches no-ops.
Inject them via _device_boundaries (level-2 record with foreign host
geometry; non-None level-1 record). set_jet_amplitude docstring names
the public jets view.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/CelerisLab/lbm/refinement_stepper.py

@@ -640,7 +640,7 @@ class FixedPatchStepper:
             return candidate
 
     def set_jet_amplitude(self, index, amplitude, *, level):
-        """Replace Jet ``index`` of ``level_jets[level]`` between steps; no geometry/table rebuild.
+        """Replace Jet ``index`` of level ``level`` (``jets[level]``) between steps; no table rebuild.
 
         Invalid input raises before any change. A device/sync error marks the
         instance failed (as step/initialize do); host state commits only after

tests/unit/test_runtime_child_remap.py

@@ -1,5 +1,6 @@
 """CPU mocks execute production remap lifecycle; no GPU numerical claim."""
 from dataclasses import replace
+from types import SimpleNamespace
 import unittest
 from unittest.mock import patch
 
@@ -69,10 +70,11 @@ class RuntimeChildRemap(unittest.TestCase):
         run._status = 'ready'
         for bad in ([], [(40,16,48,40)], [(16,16,32,24),(16,27,32,55)]):
             with self.assertRaises(ValueError): run.remap_finest(bad)
-        hosts, pairs = run.boundaries, run.hierarchy.pairs
+        records, pairs = run._device_boundaries, run.hierarchy.pairs
         for attribute, value in (('_wall_aware', True),
-                                 ('_boundaries', [*hosts[:2], object()]),        # child boundary
-                                 ('_boundaries', [hosts[0], object(), hosts[2]]),  # fine boundary
+                                 # level-2 record whose host geometry differs from objects=()
+                                 ('_device_boundaries', [*records[:2], SimpleNamespace(host=object(), jets=())]),
+                                 ('_device_boundaries', [records[0], object(), records[2]]),  # level-1 body
                                  ('hierarchy', replace(run.hierarchy, pairs=(pairs[0], None)))):
             with patch.object(run, attribute, value):
                 with self.assertRaises(ValueError): run.remap_finest(B)