feat: adopt lumped mass and reduced-coordinate shell HHT

Integrate Hex8 mass verification and fixed-null-basis shell dynamics with numerical and physics handoff evidence. Preserve interrupted reference and full-validation status; full integration validation is deferred until after performance optimization.

tests/test_compare_hht_dynamic.py

@@ -37,7 +37,7 @@ def artifacts(tmp_path_factory):
         metadata = file.create_group("metadata")
         metadata.attrs.update({
             "feature_id": "hht-implicit-dynamics", "analysis_procedure": "hht-implicit-dynamics",
-            "mass_formulation": "consistent-kinetic", "internal_formulation": "FESA-MITC4-total-lagrangian",
+            "mass_formulation": "nodal-lumped-kinetic", "internal_formulation": "FESA-MITC4-total-lagrangian",
             "initial_state": "zero-q-v-step-load-0+",
             "acceleration_convention": "physical-endpoint-and-auxiliary-separated",
             "source_step_name": "Step-1", "step_name": "Step-1", "unit_system_label": "consistent-input-units",
@@ -71,6 +71,55 @@ def changed_result(tmp_path, artifacts):
     return target
 
 
+def reduced_result(tmp_path, artifacts):
+    path = changed_result(tmp_path, artifacts)
+    with h5py.File(path, "r+") as file:
+        file["metadata"].attrs.modify("schema_version", np.uint64(2))
+        file["metadata"].attrs["time_integration_formulation"] = (
+            "reduced-coordinate-HHT-with-physical-rate-reconstruction")
+        for frame in range(101):
+            root = f"steps/Step-1/frames/{frame}/nodal"
+            displacement = file[f"{root}/displacement"]
+            displacement.attrs.modify("schema_version", np.uint64(2))
+            auxiliary = file.create_dataset(f"{root}/algorithmic_acceleration",
+                                            data=np.zeros((729, 6), dtype="<f8"))
+            for name, value in displacement.attrs.items():
+                auxiliary.attrs[name] = value
+            auxiliary.attrs["component_names"] = "AUX1,AUX2,AUX3,AUX4,AUX5,AUX6"
+            auxiliary.attrs["coordinate_system"] = "fixed-initial-global-chart"
+            auxiliary.attrs["component_unit_dimensions"] = (
+                "length/time^2,length/time^2,length/time^2,1/time^2,1/time^2,1/time^2")
+            auxiliary.attrs["quantity_semantics"] = (
+                "full-chart-HHT-filter-combination-not-predictor-driver")
+    return path
+
+
+def test_reduced_schema_preserves_displacement_comparison(tmp_path, artifacts):
+    result = comparator.compare(artifacts[0], artifacts[1], reduced_result(tmp_path, artifacts))
+    assert result["precheck"]["passed"], result["precheck"]
+    assert result["verdict"] == "passed"
+
+
+@pytest.mark.parametrize("mutation", ["missing_A", "A_semantics", "A_version", "A_nan", "method"])
+def test_reduced_schema_rejects_inconsistent_auxiliary_history(tmp_path, artifacts, mutation):
+    path = reduced_result(tmp_path, artifacts)
+    with h5py.File(path, "r+") as file:
+        auxiliary = file["steps/Step-1/frames/99/nodal/algorithmic_acceleration"]
+        if mutation == "missing_A":
+            del file[auxiliary.name]
+        elif mutation == "A_semantics":
+            auxiliary.attrs["quantity_semantics"] = "auxiliary-HHT-chart-acceleration"
+        elif mutation == "A_version":
+            auxiliary.attrs.modify("schema_version", np.uint64(1))
+        elif mutation == "A_nan":
+            auxiliary[0, 0] = float("nan")
+        else:
+            file["metadata"].attrs["time_integration_formulation"] = "full-coordinate-HHT"
+    result = comparator.compare(artifacts[0], artifacts[1], path)
+    assert not result["precheck"]["passed"]
+    assert result["families"] == []
+
+
 def test_original_csv_exact_matching_history_and_deterministic_report(artifacts):
     first = comparator.compare(*artifacts)
     second = comparator.compare(*artifacts)
@@ -128,7 +177,7 @@ def test_hdf5_precheck_rejects_before_tolerance(tmp_path, artifacts, mutation, c
         if mutation in {"procedure", "mass", "coefficient", "initial_convention", "input_content"}:
             key, value = {
                 "procedure": ("analysis_procedure", "linear-static"),
-                "mass": ("mass_formulation", "lumped"),
+                "mass": ("mass_formulation", "consistent-kinetic"),
                 "coefficient": ("alpha", 0.0),
                 "initial_convention": ("initial_state", "unloaded"),
                 "input_content": ("source_input_identity", "wrong-content"),