fix: ensure newline before heredoc closing delimiter

head -c 8000 can truncate mid-line, leaving no trailing newline.
The closing delimiter then appears on the same line as content
and GitHub Actions fails to recognize it. Add an explicit echo
to guarantee the delimiter is on its own line.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: lpcox