The welcome dashboard's updates card showed "Sovran_SystemsOS keeps
itself current" whenever no updates were pending. Nothing in the OS
auto-updates: the Hub only *checks* for updates (on load and every
30 minutes while the Hub is open); applying an update is a manual
"Update System" action followed by a reboot. The sub-line promised
behavior that does not exist.
Tie "up to date" to the last check instead ("Last check found no
updates · Click to check again"), matching the actionable phrasing
of the card's other states ("Click to review and update", "Click to
retry the update").
Also add a "Checking for updates" state for the first paint, so the
card never claims "up to date" before the first /api/updates/check
has returned.