student_manager 教学示例：菜单/工具栏加「删除选中」action（函数体待实现）

「记录」菜单与工具栏新增 actRemoveSelected（删除选中），connect 到 onRemoveSelected
槽。注意：onRemoveSelected() 函数体当前为空（实现被注释），仅完成 action 注册与
连接——槽逻辑（按选中行倒序 removeRow）留作课堂练习或后续补全，先占位。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/teaching/examples/student_manager/qt_student_manager.cpp

@@ -122,6 +122,7 @@ public:
         auto* actAdd = new QAction(QStringLiteral("添加记录"), this);
         auto* actSave = new QAction(QStringLiteral("保存"), this);
         auto* actLoad = new QAction(QStringLiteral("读取"), this);
+        auto* actRemoveSelected = new QAction(QStringLiteral("删除选中"), this);
         m_actImport = new QAction(QStringLiteral("后台导入"), this);
         auto* actAbout = new QAction(QStringLiteral("关于"), this);
 
@@ -131,12 +132,14 @@ public:
         QMenu* recordMenu = menuBar()->addMenu(QStringLiteral("记录(&R)"));
         recordMenu->addAction(actAdd);
         recordMenu->addAction(m_actImport);
+        recordMenu->addAction(actRemoveSelected);
         menuBar()->addMenu(QStringLiteral("帮助(&H)"))->addAction(actAbout);
 
         QToolBar* bar = addToolBar(QStringLiteral("main"));
         bar->addAction(actAdd);
         bar->addAction(actSave);
         bar->addAction(actLoad);
+        bar->addAction(actRemoveSelected);
         bar->addAction(m_actImport);
 
         // QAction 显示出来 ≠ 生效：忘 connect 就是「菜单点了没反应」（Day3 坑卡）
@@ -144,6 +147,7 @@ public:
         connect(actSave, &QAction::triggered, this, [this] { saveTo(m_dataPath); });
         connect(actLoad, &QAction::triggered, this, [this] { loadFrom(m_dataPath); });
         connect(m_actImport, &QAction::triggered, this, &MainWindow::onImport);
+        connect(actRemoveSelected, &QAction::triggered, this, &MainWindow::onRemoveSelected);
         connect(actAbout, &QAction::triggered, this, [this] {
             QMessageBox::about(this, QStringLiteral("关于"),
                                QStringLiteral("Day5 综合案例参考实现：Day1–4 全部知识点的收束。"));
@@ -165,6 +169,12 @@ public:
         m_table->setItem(row, 2, new QTableWidgetItem(s.tag));
     }
 
+    void onRemoveSelected() {
+        // for (int row = m_table->selectedRows().size() - 1; row >= 0; --row) {
+        //     m_table->removeRow(m_table->selectedRows().at(row).row());
+        // }
+    }
+
     bool saveTo(const QString& path) {
         QJsonArray arr;
         for (int row = 0; row < m_table->rowCount(); ++row) {