Moving UP between hubs showed the focused card's glow immediately: the
glow paints in the root overlay, unclipped by the rail viewport, so it
flashed over the spotlight while the target row was still offscreen.
The rail now suppresses only the glow for the 250 ms vertical scroll
and lets it fade in once the row settles. FocusGlowOverlay defers
attached-portal shows out of build, which OverlayPortalController
asserts against.