Function calibrate_appearance_plane 

pub fn calibrate_appearance_plane(
    request: &PlaneCalibrationRequest,
) -> Result<CalibratedPlane, String>

Establish one measured similarity transform for the whole source, then derive the current raster’s world rectangle. A crop/rotation/DPI change only changes raster_to_source and raster_size; it never recalibrates the measured span. This computes placement only, not clipped projection or IFC mutations.