essessey v0.4.2 — the missing CI workflows

CI only. No code, no API, no behaviour change.

This repo ran pipeline.yml alone, so it was never mirrored, never archived, and
had no PR gate. Adds mirror-and-archive.yml (GitLab + Codeberg + Wayback),
issue-pull.yml, and collaborators-only.yml, each on cron slots belonging to
this repo rather than copied from a sibling.