feat(release): release-pending-publish answers whether a version's publish is in flight

The new read-only `in-flight` mode reads the runs of release.yml that the
in_progress and queued filters list, plus the push run at the version commit,
and answers in-flight while another run holds that version's publish job in a
state other than completed or waiting. Any answer it cannot read answers
in-flight with reason unreadable. It runs over the dry-run HTTP layer, so a
non-GET cannot leave it. A new self-test battery pins it (12 cases).

Claude-Session: https://claude.ai/code/session_01T9u38rswFp5Rw8DswRUReJ
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude