When a user reconnects to a draft room (socket reconnect, tab visibility
return, etc.), there was a gap between when the socket connected and when
the full draft state sync arrived. The ConnectionOverlay vanished instantly
on reconnect, showing potentially stale data.
Add an isSyncing flag that keeps the overlay visible with "Syncing Draft
State..." messaging until the actual data arrives via socket or HTTP
revalidation. A 5-second safety timeout prevents the overlay from getting
stuck.
Fixes#78
5a455e6cae