fix(preprocess): initialize fresh DWH writers safely

harness/tests/test_dwh_preprocess_job.py

@@ -97,6 +97,61 @@ def test_writer_rejects_unbound_legacy_artifacts_before_building(tmp_path):
     assert not (tmp_path / ".tht-dwh" / "OWNER.json").exists()
 
 
+def test_writer_rejects_dangling_legacy_symlinks_before_claim_or_callback(tmp_path):
+    import pytest
+
+    legacy = tmp_path / "artifacts" / "mschema" / "physical.yaml"
+    legacy.parent.mkdir(parents=True)
+    legacy.symlink_to(tmp_path / "missing-catalog")
+    calls = []
+    pipeline = DwhPreprocessPipeline(
+        workspace_id="demo", workspace_root=tmp_path,
+        config_fingerprint=FP, input_fingerprint=FP,
+        introspect=lambda output: calls.append("called"),
+        build_lsh=lambda physical, output: None,
+        current_physical=legacy,
+    )
+    with pytest.raises(Exception, match="legacy artifacts are unbound"):
+        pipeline.run()
+    assert calls == []
+    assert not (tmp_path / ".tht-dwh" / "OWNER.json").exists()
+
+
+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
+
+    real_replace = module.os.replace
+    moved = tmp_path / "locked-root"
+    replacement = tmp_path / ".tht-dwh"
+    swapped = False
+
+    def swapping_replace(source, destination, *args, **kwargs):
+        nonlocal swapped
+        if destination == "OWNER.json" and kwargs.get("dst_dir_fd") is not None:
+            swapped = True
+            replacement.rename(moved)
+            replacement.mkdir(mode=0o700)
+        return real_replace(source, destination, *args, **kwargs)
+
+    monkeypatch.setattr(module.os, "replace", swapping_replace)
+    pipeline = DwhPreprocessPipeline(
+        workspace_id="demo", workspace_root=tmp_path,
+        config_fingerprint=FP, input_fingerprint=FP,
+        introspect=lambda output: (_ for _ in ()).throw(AssertionError("callback called")),
+        build_lsh=lambda physical, output: None,
+    )
+    with pytest.raises(Exception):
+        pipeline.run()
+    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
+
+
 def test_owner_requires_exact_read_only_owner_mode_and_active_requires_binding(tmp_path):
     import pytest