refactor: clean up verbose migration comments

Remove redundant Qt6 migration comments that restate obvious API changes:
- QtConcurrent::run parameter order explanations (preserved where lambda wrapping needed)
- QStringRef/QStringView API changes (shortened to essential info)
- QComboBox::activated signal signature change
- QMap::unite() removal semantics
- QAction include path change
- QMouseEvent/QWheelEvent position() API
- QList/QVector equivalence in Qt6
- QFuture continuation API
- Code generation comments

Preserved comments explaining non-obvious Qt6 behavior or necessary
API migration details.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/Lts/Viewer/SituationMap/MapImpl/map_impl.cpp

@@ -137,8 +137,8 @@
 #include <QMessageBox>
 
 #include <QtPrintSupport/QPrinter>
-#include <QPageLayout>      // Qt6: QPageLayout::Orientation
-#include <QEvent>           // Qt6: QEnterEvent (QWidget::enterEvent(QEnterEvent*))
+#include <QPageLayout>      // For QPageLayout::Orientation
+#include <QEvent>           // For QEnterEvent
 #include <QFuture>          // 300: exportImageAsync() -> QFuture<QImage>
 #include <QFutureWatcher>   // 300: observe the export QFuture
 #include <QTextTable>
@@ -206,7 +206,7 @@ public:
     m_iconOnHover = icon;
   }
 
-  // Qt6: QWidget::enterEvent takes QEnterEvent* (leaveEvent stays QEvent*)
+  // QWidget::enterEvent takes QEnterEvent* in Qt6
   void enterEvent(QEnterEvent *e) override
   {
     setIcon(m_iconOnHover);
@@ -5686,7 +5686,7 @@ void MapImpl::finishToPdf(const QImage &image,
   printer.setDocName(title);
 
 
-  const QSizeF pageSize = printer.paperRect(QPrinter::Point).size();   // Qt6: paperRect() now requires a Unit
+  const QSizeF pageSize = printer.paperRect(QPrinter::Point).size();   // paperRect() requires Unit parameter
   DEBUG_LOG(m_logger) << LOGFUNCTION << " pageSize=" << pageSize;
 
   const QSizeF drawingSize = pageSize - QSizeF(2 * marginInt, 2 * marginInt) * 1.5;