fix: 修复横线撤销后无法再次插入

app/src/ui/logic_editor_widget.cpp

@@ -1124,6 +1124,17 @@ void LogicEditorWidget::reloadLogic()
         scene_->setSceneRect(0, 0, kMinimumSceneWidth, 400);
         return;
     }
+    const bool current_rung_exists = std::any_of(
+        logic->rungs.cbegin(), logic->rungs.cend(),
+        [this](const LadderRung &rung)
+        {
+            return rung.id == current_rung_id_;
+        });
+    if (!current_rung_id_.empty() && !current_rung_exists)
+    {
+        // 撤销或重做可能移除当前网络，不能把过期 ID 继续传给编辑服务
+        current_rung_id_.clear();
+    }
     if (current_rung_id_.empty() && !logic->rungs.empty())
     {
         current_rung_id_ = logic->rungs.front().id;

app/tests/main_window_tests.cpp

@@ -1023,6 +1023,39 @@ void testLogicContinuousInsertionConsumesFullWire()
             "the toolbar must reject only the eleventh condition after all wires are consumed");
 }
 
+void testLogicHorizontalWireCanBeInsertedAgainAfterUndoingFirstAutoRung()
+{
+    TestProjectStorage storage;
+    ProjectService project_service(storage);
+    LogicEditorService service(project_service);
+    const std::string logic_id = service.ensureDefaultLogic().id;
+    LogicEditorWidget editor(service);
+    editor.setLogicId(logic_id);
+    editor.resize(1400, 360);
+    editor.show();
+    QApplication::processEvents();
+
+    require(editor.addHorizontalWire().succeeded,
+            "the first horizontal wire must create the initial ladder network");
+    const ControlLogic *logic = service.findLogic(logic_id);
+    require(logic != nullptr && logic->rungs.size() == 1U,
+            "the first horizontal wire must leave one network in the model");
+
+    require(service.undo().succeeded,
+            "undo must remove the automatically created network");
+    editor.reloadLogic();
+    logic = service.findLogic(logic_id);
+    require(logic != nullptr && logic->rungs.empty(),
+            "undo must restore the initially empty ladder logic");
+
+    require(editor.addHorizontalWire().succeeded,
+            "a horizontal wire must be insertable again after undoing the first one");
+    logic = service.findLogic(logic_id);
+    require(logic != nullptr && logic->rungs.size() == 1U
+                && logic->rungs.front().condition.has_value(),
+            "reinserting the horizontal wire must create a fresh network");
+}
+
 void testWindowTitleTracksUnsavedProjectChanges()
 {
     TestProjectStorage storage;
@@ -2446,6 +2479,7 @@ int main(int argc, char *argv[])
         testLogicParallelPaddingGridInsertion();
         testLogicParallelBranchConnectsShortBranchToRightJoin();
         testLogicContinuousInsertionConsumesFullWire();
+        testLogicHorizontalWireCanBeInsertedAgainAfterUndoingFirstAutoRung();
         testWindowTitleTracksUnsavedProjectChanges();
         testModeActionsControlEditingAvailability();
         testRuntimeMonitorWindowLifecycle();