test: bind Simulation usability guard on host doubles

tests/unit/test_jets.py

@@ -194,6 +194,7 @@ def test_public_surface_exchange_for_jet_preserves_aperture_at_zero_and_reverse(
     field, bodies = jet_case(device, [jet])
     sim = SimpleNamespace(bodies=bodies, field=field, _initialized=True,
                           stream=SimpleNamespace(synchronize=device.synchronize))
+    sim._require_usable = Simulation._require_usable.__get__(sim)
     cl = field.curved
     assert bodies.get(0).surface_actuation is None
     aperture, velocity = cl.aperture, cl.surface_velocity.copy()
@@ -218,6 +219,7 @@ def test_public_surface_exchange_keeps_legacy_and_passive_guards(device):
     bodies.sync_to_gpu(field)
     sim = SimpleNamespace(bodies=bodies, field=field,
                           stream=SimpleNamespace(synchronize=device.synchronize))
+    sim._require_usable = Simulation._require_usable.__get__(sim)
     for value in Simulation.read_surface_exchange(sim, 0).values():
         np.testing.assert_array_equal(value, 0.)
     field.curved.free_gpu_columns()

tests/unit/test_state_regressions.py

@@ -295,6 +295,7 @@ def test_passive_overlap_failure_keeps_live_state(device, entry, second_x):
                           _initialized=entry == "runtime_edit",
                           _assert_allocation_contract=lambda: None,
                           stream=SimpleNamespace(synchronize=device.synchronize))
+    sim._require_usable = Simulation._require_usable.__get__(sim)
     with pytest.raises(ValueError, match="active fluid receivers|unique cut-link writers"):
         if entry == "sync":
             bodies.sync_to_gpu(field)