Backing out to home selected the home tab but let focusActiveTabIfReady
steal real focus into the content while _isSidebarFocused stayed true,
leaving the rail stuck expanded over a shifted content box that clipped
the end of every hub row. Skip the content-focus grab while the sidebar
owns focus, move the sidebar focus ring to the Home item on back-to-home,
and self-heal the flag whenever the content scope actually gains focus.
close#1411
edde746
6af4289289