--instance NAME on the shell entry points through scripts/instance.sh;
per-instance config, data root and marker, units, wrapper and ports;
the claim checks in mosaic-config.mjs; the guard protects every
instance's config and data root. Brief blob 4e8f1e0528, design
agents/darkwing/work/queue-190/DESIGN.md rev 3 (Filbert approved).
