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/tests/test_viewshed3d.cpp

@@ -73,7 +73,7 @@ TEST(Viewshed3DTest, ViewshedLocation_BasicOperations)
 // Test Viewshed3D Qt6 QMouseEvent API
 TEST(Viewshed3DTest, Qt6_QMouseEvent_API)
 {
-    // Qt6: QMouseEvent globalPosition() returns QPointF
+    // QMouseEvent::globalPosition() returns QPointF in Qt6
     // This test verifies the pattern used in ViewshedLocation.cpp
     
     // Create a mock mouse event position
@@ -86,7 +86,7 @@ TEST(Viewshed3DTest, Qt6_QMouseEvent_API)
     EXPECT_DOUBLE_EQ(localPos.x(), 50.0);
     EXPECT_DOUBLE_EQ(localPos.y(), 75.0);
     
-    // Qt6: Use globalPosition() instead of globalX()/globalY()
+    // Use globalPosition() in Qt6
     // In actual code: event->globalPosition().x(), event->globalPosition().y()
     double globalX = globalPos.x();
     double globalY = globalPos.y();
@@ -98,7 +98,7 @@ TEST(Viewshed3DTest, Qt6_QMouseEvent_API)
 // Test Viewshed3D Qt6 QWheelEvent API
 TEST(Viewshed3DTest, Qt6_QWheelEvent_API)
 {
-    // Qt6: QWheelEvent position() and globalPosition() return QPointF
+    // QWheelEvent position()/globalPosition() return QPointF
     // This test verifies the pattern used in ViewshedLocation.cpp
     
     QPointF position(150.0, 250.0);
@@ -110,7 +110,7 @@ TEST(Viewshed3DTest, Qt6_QWheelEvent_API)
     EXPECT_DOUBLE_EQ(globalPosition.x(), 200.0);
     EXPECT_DOUBLE_EQ(globalPosition.y(), 300.0);
     
-    // Qt6: Use position() instead of x()/y()
+    // Use position() in Qt6
     double posX = position.x();
     double posY = position.y();
     
@@ -121,7 +121,7 @@ TEST(Viewshed3DTest, Qt6_QWheelEvent_API)
 // Test Viewshed3D Qt6 QTouchEvent API
 TEST(Viewshed3DTest, Qt6_QTouchEvent_API)
 {
-    // Qt6: QTouchEvent points() returns list of touch points
+    // QTouchEvent::points() returns list in Qt6
     // This test verifies the pattern used in ViewshedLocation.cpp
     
     // Simulate touch points
@@ -138,7 +138,7 @@ TEST(Viewshed3DTest, Qt6_QTouchEvent_API)
     
     EXPECT_EQ(touchPoints.size(), 2);
     
-    // Qt6: Use points() to access touch points
+    // Access touch points via points() in Qt6
     // In actual code: for (const auto& point : event->points())
     for (const auto& point : touchPoints)
     {
@@ -156,7 +156,6 @@ TEST(Viewshed3DTest, Qt6_QTouchEvent_API)
 // Test Viewshed3D Qt6 container operations
 TEST(Viewshed3DTest, Qt6_Container_Operations)
 {
-    // Qt6: QList and QVector are identical
     QList<double> elevations;
     elevations << 100.0 << 200.0 << 300.0 << 400.0 << 500.0;