Run launches the live-view TUI and the Runner concurrently. It blocks
until the user quits the TUI (q / ctrl+c) or the Runner finishes and
the user dismisses the screen.
Runner is the function that performs the migration work in a goroutine
while the TUI runs in the foreground. It receives the sink to install
on its Queen instance and is expected to return when migrations finish
(or fail). The error is surfaced in the TUI footer.