--link-journal=host bind-mounts a host directory journald never
writes into for this container (empty, root:nogroup, confirmed on
the live host — #4527). Dropping it falls back to nixpkgs' default
--link-journal=try-guest, the same shape every agent container
already uses, so the in-container collector's journald receiver
(directory = /var/log/journal) now reads a journal that is actually
written.
merge stays true and services.hyperhive.swarm.otel.journaldUnits is
untouched so this deploy changes exactly one thing; comments that
described the old host-linked shape are rewritten to match.
Adds a module-eval assertion (bao-otel-collector.nix) that the
container's extraFlags never re-add --link-journal=host.
Refs #4527, #4499.
44009dc51d