run-discord-scrape-host.sh runs verify --disk-only before preflight/scrape
so setup-cron monthly jobs fail fast when archive roots are low on space.
Harden bootstrap smoke to surface failures when dry-run fails.
Fail fast when archive or repo paths lack free space (DCE_MIN_FREE_MB),
treat disk-full export failures as skippable channels, and add an offline
disk-space smoke. Smokes default DCE_MIN_FREE_MB=0 so CI stays portable.