behavior change: navigating to a different-aspect image/video while
tiled then un-tiling now resizes the floating window to the current
content's aspect and resets the image viewer zoom. Previously the
window restored to the old floating geometry with the wrong aspect
locked.
Stash content dims on the tiled early-return in _fit_to_content, then
detect the tiled-to-floating transition via a debounced resizeEvent
check that re-runs the fit.
pax
2cdab574ca