Mark real multi-device tests with @pytest.mark.multi_device

test_distribution and test_layout_map_mesh_shapes were not marked, so the
dedicated multi_device CI job (added in keras-team#2809, filtering on
-m "multi_device and not kaggle_key_required and not extra_large") would
never collect any real test from this model, staying green while doing
nothing. test_layout_map_live_presets already carries the marker (plus
kaggle_key_required + extra_large) and is left as-is, correctly excluded
from this job by design.

For test_layout_map_mesh_shapes, the marker is placed as the innermost
decorator (directly above the function, below
@parameterized.named_parameters(...)), not outermost: absl.testing.parameterized
expands each parameter case into a new function via functools.wraps, which
only copies attributes already present on the wrapped function's __dict__
at expansion time. Placing pytest.mark above named_parameters sets
pytestmark on the intermediate _ParameterizedTestIter object, which is
discarded once the metaclass expands per-case methods, silently losing the
marker on every generated case. Verified empirically via --collect-only:
outer placement collected 0 of 12 parameterized cases under
-m multi_device; inner placement collects all 12.

Author: pctablet505

keras_hub/src/models/qwen3_5_moe/qwen3_5_moe_backbone_test.py

@@ -230,6 +230,7 @@ def test_auxiliary_loss(self):
         for loss in model.losses:
             self.assertGreater(loss, 0.0, "Auxiliary loss should be positive")
 
+    @pytest.mark.multi_device
     def test_distribution(self):
         # The default config keeps num_key_value_heads=2 (not divisible by
         # every host's device count) and includes both a linear_attention and
@@ -295,6 +296,7 @@ def test_distribution(self):
         for dims in (QWEN3_5_MOE_35B_A3B_DIMS, QWEN3_5_MOE_SMALL_DIMS)
         for shape in CAPPED_MESH_SHAPES
     )
+    @pytest.mark.multi_device
     def test_layout_map_mesh_shapes(self, dims, mesh_shape):
         if keras.backend.backend() != "jax":
             self.skipTest("`ModelParallel` testing requires the Jax backend.")