Swarm's nested DinD-node daemons plus the backup DR drill (LUKS loop image,
per-node registry pulls) fill the ~50 GB root fs and trip the <6 GB abort
guard in utils/tests/swarm/matrix.py, while /mnt is a separate ~74 GB
partition sitting idle behind only a swapfile.
Add a runner step that moves the host Docker data-root to /mnt/docker when
/mnt is a separate, roomier partition (detection mirrors enlarge_swap.sh),
before any Docker usage. Best-effort: any failure rolls Docker back onto /
and the step still exits 0, so it can never turn a green deploy red. Wired
into the compose, swarm, and host deploy workflows.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>