fix(simulation): export ACTIVE valves correctly for EPANET 2

The legacy online simulation path still exported internal ACTIVE states as STATUS keywords, which EPANET 2 rejects. Preserve numeric settings and EPANET 3 output while passing the format through both exporters. Surface the original engine error inside the model transaction so failed runs roll back before result storage.

Regression guard: six failures reproduced on the deployed baseline, including native input validation. All 34 focused export, service and endpoint checks pass after the fix; the real project also returns native node and link results.

tests/unit/test_analysis_simulation.py

@@ -277,3 +277,51 @@ def test_extended_simulation_marks_run_failed_when_result_storage_fails(monkeypa
         )
 
     assert [call[1]["status"] for call in lifecycle_calls] == ["failed"]
+
+
+@pytest.mark.parametrize("has_output", [False, True])
+def test_engine_failure_preserves_report_and_rolls_back_model_changes(monkeypatch, has_output):
+    from app.services import simulation
+
+    transaction_outcome = []
+
+    @contextmanager
+    def project_transaction(_name):
+        try:
+            yield
+        except Exception:
+            transaction_outcome.append("rollback")
+            raise
+        else:
+            transaction_outcome.append("commit")
+
+    monkeypatch.setattr(simulation, "project_transaction", project_transaction)
+    monkeypatch.setattr(simulation, "get_time", lambda _: {
+        "HYDRAULIC TIMESTEP": "0:15:00",
+        "DURATION": "0:00",
+        "PATTERN START": "0:00",
+    })
+    monkeypatch.setattr(simulation, "set_time", lambda *_: None)
+    result = {
+        "simulation_result": "failed",
+        "report": "EPANET report\n  Error 202: illegal numeric value ACTIVE in [STATUS] section:\n  V1 ACTIVE\n",
+    }
+    if has_output:
+        result["output"] = {"node_results": [], "link_results": [], "times": {"num_periods": 1}}
+    monkeypatch.setattr(simulation, "run_project", lambda _: json.dumps(result))
+    refresh = Mock()
+    store = Mock()
+    monkeypatch.setattr(simulation, "refresh_materialized_views_after_commit", refresh)
+    monkeypatch.setattr(simulation.TimescaleInternalStorage, "store_realtime_simulation", store)
+
+    with pytest.raises(RuntimeError, match="EPANET.*Error 202"):
+        simulation.run_simulation(
+            name="demo",
+            simulation_type="realtime",
+            modify_pattern_start_time="2026-07-30T04:30:00Z",
+            scada_mappings=_empty_scada_mappings(simulation),
+        )
+
+    assert transaction_outcome == ["rollback"]
+    refresh.assert_not_called()
+    store.assert_not_called()