`secret generate mnemonic`, `secret vault list` and `secret unlocker list`,
in text and `--json` form, printed through cobra's `cmd.Println` and
`cmd.Printf`. Those write to stderr when no output writer is set, and the
binary sets none, so a pipe or `$(...)` got nothing. They now write to
`cmd.OutOrStdout()`, as `secret list` does, and so does "No versions found"
from `secret version list`. Status messages and the warning printed after
the mnemonic stay on stderr.
A new test runs the built binary and reads the stdout of `generate
mnemonic` and of both listings in both forms.
Model: opus-5-5
sneak