Silence the fork-safety warning from num_workers>0 pipeline tests

The two DataLoader-num_workers quota tests are the only ones in the file
that leave num_workers>0, so they're the only ones that actually spawn
forked worker subprocesses under pytest's multi-threaded process and hit
Python's fork-safety DeprecationWarning. The thing under test is just the
pre-flight quota-check message, emitted before the DataLoader is built.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_pipeline.py

@@ -186,14 +186,19 @@ def test_run_train_job_no_topn_map_for_physical_target(tmp_path, data):
     assert loaded.topn_maps == {}
 
 
+@pytest.mark.filterwarnings("ignore::DeprecationWarning:multiprocessing.popen_fork")
 def test_run_train_job_warns_when_num_workers_exceeds_shared_quota(
     tmp_path, data, monkeypatch
 ):
+    # num_workers>0 makes DataLoader actually fork worker subprocesses
+    # (unlike every other test here, which runs with num_workers=0) — pytest
+    # itself is multi-threaded, hence Python's fork-safety warning below.
     monkeypatch.setattr("giant.pipeline.os.cpu_count", lambda: 8)  # quota = 2
     echo = _run(data, tmp_path / "out", num_workers=3)
     assert any("num-workers=3" in m and "exceeds" in m for m in echo)
 
 
+@pytest.mark.filterwarnings("ignore::DeprecationWarning:multiprocessing.popen_fork")
 def test_run_train_job_no_warning_when_num_workers_within_shared_quota(
     tmp_path, data, monkeypatch
 ):