GetSecret and GetSecretWithVersion discarded the result of writing the
value to stdout, so a full disk or a failing stdout left the caller with
an empty or cut-short file and exit status 0. The write error is now
returned, so the command prints it and exits 1.
Deviation: a stdout the shell closed before `secret` started still exits
0, because the Go runtime opens /dev/null in its place and the write
there succeeds.
Model: opus-5-5
sneak