shots property
Where the two frames are filed, as ShotCache keys.
The verdict is not the picture, and a reader wants both. Without this a comparison could say a preview changed by 0.38% and nothing anywhere could show it: the keys are computed inside the runner from a closure fingerprint nobody outside can reproduce. They go in the artifact too, so a panel, an agent and a static page all address the same two files.
Implementation
final ({String base, String head})? shots;