Topbar belongs to the window now: it carries the open-repo strip,
switcher and account. The page tree for the current scope moved
into the shell (`ShellNav`), so org pages keep their nav on mobile
where the footer is the tab strip.
Tabs persist to localStorage, keyed off the matched /$org/$repo
route rather than the pathname so /$org/home and /admin/* can't
open one. Each tab remembers its own last page.
- drop OrgSubnav, folded into ShellNav
- MobileFooter is now just the tab strip
- org Settings link stays on the current page instead of
bouncing to /$org/home
- dark --surface-1 #171717 -> #1f1f21
