Bash: ssh -n silently drops a heredoc'd remote script, and an empty path turns 'scp -r host:' into a home-dir copy

Two shell pitfalls that combined in an automation runner. (1) ssh -n host bash -s <<EOF ... EOF runs nothing: -n redirects stdin from /dev/null, so the heredoc never reaches the remote shell and the command exits 0. Either drop -n when feeding stdin, or copy a script file to the host and run it by path. (2) scp -r "host:$SRC" dest with an empty SRC becomes scp -r host: dest, which copies the remote user's whole home directory. Guard every remote path: : "${SRC:?}", require it to be absolute and under the expected run directory, and copy an explicit file list rather than a directory. Test the runner against fake and empty paths before using it on a shared host, because bash -n catches neither of these.