`[scope-probe]` grows the two readings a "blank scope window" report needs before it can be
blamed: `empty_drop=`/`empty_slot0=` (the same drop onto the empty window, the user's own
path) and `gl copy=/gl empty=/gl detached ok= frames=` -- each window's adapter context
status and staged-frame count. A scope whose context failed draws nothing at all: no axes,
no traces, exactly the "blank plot widget, no x axis" report -- and that is a driver/context
finding, not a layout one. The detached window is left open by the probe, so a run's
screenshots can answer "does the detached figure draw" with pixels.
Martino Ferrari
b90a99ec39