The session-manager wiring (uwsm + the Hyprland Wayland-compositor
entry that gives Hyprland a proper graphical-session.target so user
services like nomarchy-wallpaper, walker, and elephant chain off it)
had lived in core/system/virtualization.nix by historical accident —
loaded unconditionally on every install, nothing to do with libvirt
or docker.
Lifted into a dedicated core/system/session.nix and imported from
core/system/default.nix between systemd.nix and virtualization.nix.
virtualization.nix now contains only the libvirt + docker branches
its filename implies.
`nix flake check --no-build` clean. No behaviour change.
