fix(preprocess): retain DWH root fd through lease

harness/tests/test_dwh_preprocess_job.py

@@ -120,7 +120,6 @@ def test_writer_rejects_dangling_legacy_symlinks_before_claim_or_callback(tmp_pa
 def test_owner_publication_remains_on_locked_root_when_path_is_swapped(
     monkeypatch, tmp_path,
 ):
-    import os
     import pytest
     import tht.jobs.dwh_pipeline as module
 
@@ -135,6 +134,7 @@ def test_owner_publication_remains_on_locked_root_when_path_is_swapped(
             swapped = True
             replacement.rename(moved)
             replacement.mkdir(mode=0o700)
+            (moved / "generation.lock").rename(replacement / "generation.lock")
         return real_replace(source, destination, *args, **kwargs)
 
     monkeypatch.setattr(module.os, "replace", swapping_replace)
@@ -149,7 +149,7 @@ def test_owner_publication_remains_on_locked_root_when_path_is_swapped(
     assert swapped
     assert (moved / "OWNER.json").is_file()
     assert not (replacement / "OWNER.json").exists()
-    assert os.stat(moved / "generation.lock").st_ino != os.stat(replacement).st_ino
+    assert (replacement / "generation.lock").is_file()
 
 
 def test_owner_requires_exact_read_only_owner_mode_and_active_requires_binding(tmp_path):