"""Service layer: orchestration of one user-facing use case per module.

Each module here answers a single question -- "install these maps",
"deploy the active mods", "scan a mod folder" -- by composing functions
from `core.io` and `core.domain`. This is the layer the routing/UI code
should call into; it should never be imported by `core.io` or
`core.domain` (that would be a layering violation).
"""