fix(interactive): prevent looping forever when input cannot be read

[npmania]

ConfirmPrompt discards the error from ReadString, so when there's no readable input the empty string hits default and loops forever.

Non-interactive runs that reach a prompt will spin. In my case topf nodes with stdin closed hit No secrets.yaml found for cluster X. Generate a new one? and wrote 575MB in 8 seconds. apply, reset, upgrade share the confirm prompt.

Not applying errors.Is(err, io.EOF) since a closed fd or a detached tty will give os.ErrClosed and EIO, which loop just the same. It will end up having to cover all kinds of cases that can occur in different environments.

I have put the check after the switch so printf 'y' | topf still works, because ReadString returns the data and io.EOF together.