fix(dwh): release snapshots before job startup

harness/tests/test_dwh_preprocess_job.py

@@ -608,6 +608,61 @@ def test_pipeline_releases_materialized_snapshot_after_every_run(tmp_path):
     assert pipeline._snapshot_holder is None
 
 
+def test_corrupt_resume_checkpoint_releases_materialized_snapshot(tmp_path):
+    import tht.jobs.dwh_pipeline as module
+    import pytest
+
+    pipeline = DwhPreprocessPipeline(
+        workspace_id="demo", workspace_root=tmp_path,
+        config_fingerprint=FP, input_fingerprint=FP,
+        introspect=lambda output: output.write_text("catalog"),
+        build_lsh=lambda physical, output: _write_lsh([], physical, output),
+    )
+    assert pipeline.run().status == "succeeded"
+    baseline = set(module._SNAPSHOT_DIRS)
+    run_id = "e" * 32
+    run_dir = tmp_path / ".tht-jobs" / "dwh" / "runs" / run_id
+    run_dir.mkdir(parents=True)
+    (run_dir / "checkpoint.json").write_text("not-json")
+
+    with pytest.raises(Exception, match="checkpoint is invalid"):
+        pipeline.run(resume_run_id=run_id)
+    assert pipeline._snapshot_holder is None
+    assert set(module._SNAPSHOT_DIRS) == baseline
+
+
+def test_job_spec_construction_failure_releases_materialized_snapshot(monkeypatch, tmp_path):
+    import tht.jobs.dwh_pipeline as module
+    import pytest
+
+    pipeline = DwhPreprocessPipeline(
+        workspace_id="demo", workspace_root=tmp_path,
+        config_fingerprint=FP, input_fingerprint=FP,
+        introspect=lambda output: output.write_text("catalog"),
+        build_lsh=lambda physical, output: _write_lsh([], physical, output),
+    )
+    assert pipeline.run().status == "succeeded"
+    baseline = set(module._SNAPSHOT_DIRS)
+    captured = []
+    real_materialize = module._materialize_generation_fd
+
+    def capture(*args, **kwargs):
+        holder, root = real_materialize(*args, **kwargs)
+        captured.append(holder)
+        return holder, root
+
+    monkeypatch.setattr(module, "_materialize_generation_fd", capture)
+    monkeypatch.setattr(
+        module, "JobSpec",
+        lambda **kwargs: (_ for _ in ()).throw(RuntimeError("job spec injected")),
+    )
+    with pytest.raises(RuntimeError, match="job spec injected"):
+        pipeline.run()
+    assert pipeline._snapshot_holder is None
+    assert set(module._SNAPSHOT_DIRS) == baseline
+    assert captured and all(not path.exists() for path in captured)
+
+
 def test_publish_root_swap_after_lease_never_writes_replacement(monkeypatch, tmp_path):
     import tht.jobs.dwh_pipeline as module