[XPU][ci]: disable XPU NIXL disaggregation test (#40540)

.github/workflows/pr-test-xpu.yml

@@ -62,6 +62,7 @@ jobs:
               - "python/sglang/test/!(ascend|observability|mock_model|manual|external_models|kernels)/**/!(*.md)"
               - "python/pyproject_xpu.toml"
               - "test/registered/xpu/**/!(*.md)"
+              - "test/registered/disaggregation/test_disaggregation_xpu.py"
               - "test/registered/attention/test_chunk_gated_delta_rule.py"
               - "test/registered/attention/test_deterministic.py"
               - "test/registered/lora/test_moe_lora_info.py"

test/registered/disaggregation/test_disaggregation_xpu.py

@@ -24,7 +24,11 @@ from sglang.test.server_fixtures.disaggregation_fixture import (
 )
 from sglang.test.test_utils import DEFAULT_SMALL_MODEL_NAME_FOR_TEST_QWEN
 
-register_xpu_ci(est_time=300, suite="stage-b-test-1-gpu-xpu")
+register_xpu_ci(
+    est_time=300,
+    suite="stage-b-test-1-gpu-xpu",
+    disabled="XPU CI image does not include an XPU-compatible NIXL/UCX build",
+)
 
 _XPU_AVAILABLE = torch.xpu.is_available()