put() loses its MultiProgress parameter: the summary, pre-flight and
connection spinners become view messages, the per-file SFTP transfer
reports determinate progress through view.progress (upload_file takes
a byte-count callback instead of an indicatif bar), and the display is
released through view.suspend on every exit path. The hardcoded
trust-on-first-use prompt in the SSH host-key verification becomes the
Prompter::accept_host_key port (fail-closed by default; the terminal
prompter prints the authenticity banner and confirms), so a remote
frontend can surface its own host-key dialog.