Per the operator's call on #3372: rather than moving Grafana off the
forge's 3000 to another number, take it off TCP entirely.
The collision was possible because every swarm service container shares
the host's network namespace, which makes a port a swarm-wide resource
two modules can each claim believing it free — Grafana took upstream's
3000, so does the forge, and `grafana.<swarm-domain>` served the forge
with no bind error and nothing in any log. A socket has a path, and a
path collision is a build-time conflict rather than a runtime coin toss.
Three parts, none of which works alone:
- `protocol = "socket"` with `socket_gid` = nginx's static gid 60.
- Grafana joins that gid inside the container. A non-root process may
only chgrp to a group it belongs to, and a container has its own user
database — without the membership Grafana starts, the chown fails, and
the socket is simply unreachable.
- The socket dir is created host-side by tmpfiles and bind-mounted in. A
container's /run is an nspawn tmpfs, so it is not visible from the host
at /var/lib/nixos-containers/<name>/run; the same shape the per-agent
web.sock already uses.
The `port` option is gone rather than deprecated — nothing can set it to
a colliding value if it does not exist.
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