fix timeline popover

lib/components/pages/loco_timeline/timeline_grid.dart

@@ -447,13 +447,11 @@ class _ValueBlockMenu extends StatelessWidget {
       final overlay = Overlay.of(context);
       final renderBox = overlay?.context.findRenderObject() as RenderBox?;
       if (renderBox == null) return;
+      // Translate from global screen coordinates into the overlay's local space
+      // so the menu appears where the gesture happened.
+      final localPosition = renderBox.globalToLocal(globalPosition);
       final position = RelativeRect.fromRect(
-        Rect.fromLTWH(
-          globalPosition.dx,
-          globalPosition.dy,
-          1,
-          1,
-        ),
+        Rect.fromLTWH(localPosition.dx, localPosition.dy, 1, 1),
         Offset.zero & renderBox.size,
       );