A container may name networks it also joins once created, for the per-machine
setting that keeps a found network while a neighbour still resolves it there:
joined after the run, part of the spec, refused when it cannot be joined.
A declaration may say which modules the mesh left out because a stored setting
cannot compose with its definition. Absence used to read as removal; a left-out
module's records are kept and said, and its holds are not released.
Genesis raises the bootstrap forge under the gitea module's container name, with
its image digest and its data directory mounted at /data, so the module holds it
by the found rule instead of raising a second forge beside it (issue 090). The
network is the one difference left for a take to say. Before this the forge had
no volume: its repositories were the container's, lost with it.
