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_qt6_api_migrations.cpp

@@ -25,7 +25,7 @@ TEST(Qt6ApiTest, QStringView_Sliced)
     QString testString = QStringLiteral("Hello World");
     QStringView view(testString);
     
-    // Qt6: slice() -> sliced()
+    // QBitArray::sliced() in Qt6 (was slice())
     QStringView subView = view.sliced(0, 5);
     EXPECT_EQ(subView.toString(), QStringLiteral("Hello"));
     
@@ -61,7 +61,6 @@ TEST(Qt6ApiTest, QFuture_Continuation)
         return 42;
     });
     
-    // Qt6: QFuture supports .then() continuations
     QFuture<QString> continued = future.then([](QFuture<int> result) {
         return QString::number(result.result());
     });
@@ -73,7 +72,7 @@ TEST(Qt6ApiTest, QFuture_Continuation)
 // Test Qt::MiddleButton enum (Qt6 replacement for Qt::MidButton)
 TEST(Qt6ApiTest, Qt_MiddleButton_Enum)
 {
-    // Qt6: Qt::MidButton -> Qt::MiddleButton
+    // Qt::MiddleButton in Qt6 (was MidButton)
     Qt::MouseButton middleBtn = Qt::MiddleButton;
     EXPECT_EQ(middleBtn, Qt::MiddleButton);
     EXPECT_NE(middleBtn, Qt::LeftButton);
@@ -88,7 +87,7 @@ TEST(Qt6ApiTest, QVariantMap_Iteration)
     map1.insert(QStringLiteral("key2"), 2);
     
     QVariantMap map2;
-    // Qt6: Replace unite() with iterate/insert pattern
+    // QMap::unite() removed in Qt6
     for (auto it = map1.begin(); it != map1.end(); ++it)
     {
         map2.insert(it.key(), it.value());
@@ -103,8 +102,7 @@ TEST(Qt6ApiTest, QVariantMap_Iteration)
 TEST(Qt6ApiTest, QTouchEvent_API)
 {
     // This test verifies the API exists - actual touch testing requires GUI
-    // Qt6: touchPoints() -> points()
-    // Qt6: QEventPoint::screenPos() -> globalPosition()
+    // QTouchEvent::points() and QEventPoint::globalPosition() in Qt6
     
     // Create a mock test - in real code, QTouchEvent is created by system
     // We verify the types compile correctly
@@ -121,7 +119,7 @@ TEST(Qt6ApiTest, QTouchEvent_API)
 // Test QMouseEvent position API (Qt6)
 TEST(Qt6ApiTest, QMouseEvent_Position_API)
 {
-    // Qt6: event.x()/y() -> event.position().x()/y()
+    // QMouseEvent::position() in Qt6 (was x()/y())
     // Create a mouse event with Qt6 API
     QMouseEvent event(QEvent::MouseButtonPress, 
                       QPointF(100.0, 200.0),  // globalPos
@@ -142,7 +140,7 @@ TEST(Qt6ApiTest, QMouseEvent_Position_API)
 // Test QWheelEvent position API (Qt6)
 TEST(Qt6ApiTest, QWheelEvent_Position_API)
 {
-    // Qt6: event.x()/y() -> event.position().x()/y()
+    // QWheelEvent::position() in Qt6 (was x()/y())
     QWheelEvent event(QPointF(100.0, 200.0),  // pos
                       QPointF(100.0, 200.0),  // globalPos
                       QPoint(0, 0),           // pixelDelta