## Summary
`act_runner`'s default `container.force_pull: true` re-issues a `docker pull` at the start of every job, adding 10–30 s of registry round-trip even when every layer is already locally cached. With job images pinned to specific tags (`catthehacker/ubuntu:act-22.04` and `:full-22.04`), the implicit pull is pure overhead and contradicts the deliberate-upgrade policy ADR-0015 spells out for the runner image.
- Add `infra/runner-config.yaml` with `container.force_pull: false`.
- Mount it read-only into all three runners and point each at it via `CONFIG_FILE=/etc/runner/config.yaml`.
- Document the pre-pull procedure and image-upgrade playbook in `infra/README.md` → "Job image pinning and pre-pull".
- Fold the pre-pull into the "First-time registration" walkthrough so a fresh setup is correct end-to-end.
The trade-off: the runner host must hold the images locally before the runner is asked to use them. Documented.
## Roll-out (manual, on the runner host)
```bash
cd infra/
# 1. Pre-pull the job images (one-shot — pays the cold cost once).
docker pull catthehacker/ubuntu:act-22.04
docker pull catthehacker/ubuntu:full-22.04
# 2. Recreate the runners so the new mount + env var take effect.
docker compose -f ci-runners.compose.yml up -d --force-recreate
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Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #10
