The idle trim (3 s without renders) released the shared device copy of the original a zoom
window is cut from, so pausing between pans made the next pan upload it again: 800 MB for a
64 MP raw, ~1.4 s of "gpu sample" measured (5 ms when it is still there). While a Detail window
texture is held the renderer is not idle; once the windows are gone (zoomed out, another photo,
or another view, which now frees the Detail view's windows) the trim runs as before.