Feat/add fi selective state update kernel call (#18070)

Signed-off-by: Shahar Mor <smor@nvidia.com>

test/registered/layers/mamba/conftest.py

@@ -0,0 +1,19 @@
+import pytest
+
+from sglang.srt.layers.attention.mamba.ops import ssu_dispatch
+from sglang.srt.layers.attention.mamba.ops.ssu_dispatch import (
+    initialize_mamba_selective_state_update_backend,
+)
+from sglang.srt.server_args import ServerArgs
+
+
+@pytest.fixture(scope="session", autouse=True)
+def _init_mamba_ssu_backend():
+    """Initialize the Mamba SSU dispatch backend for the test session.
+
+    In production this happens in Scheduler.init_mamba_backend(). Tests have no
+    scheduler, so we do it here via the same public API.
+    """
+    initialize_mamba_selective_state_update_backend(ServerArgs(model_path="dummy"))
+    yield
+    ssu_dispatch._mamba_ssu_backend = None