[Tests] Clarify pytest skip reasons with actionable context (#32981)

Signed-off-by: 7. Sun <jhao.sun@gmail.com>

tests/v1/sample/test_topk_topp_sampler.py

@@ -48,7 +48,11 @@ def test_topk_impl_equivalence():
     assert torch.allclose(result1, result2)
 
 
-@pytest.mark.skip(reason="FIXME: This test is failing right now.")
+@pytest.mark.skip(
+    reason="FlashInfer top-k/top-p renorm comparison fails; "
+    "needs investigation of tolerance threshold or "
+    "interface differences between Python and FlashInfer implementations"
+)
 def test_flashinfer_sampler():
     """
     This test verifies that the FlashInfer top-k and top-p sampling