During baseline correction display the zone considered for median

It is not clear what is the zone that is being considered to calculate the median for anchors in baseline correction. We could maybe display this zone as a translucent rectangle.

<img width="98" height="78" alt="Image" src="https://github.com/user-attachments/assets/1c349253-b7fc-462e-9295-b00362b46d02" />