Adds the five missing worker units plus a grouping target so
`systemctl start decnet.target` brings the whole fleet up in order.
Sniffer gets CAP_NET_RAW for scapy; collector and mutator join the
docker supplementary group for docker.sock access. Repoints
Documentation= across all existing units to the canonical
git.resacachile.cl wiki.
Land the `decnet bus` worker and `get_bus()` factory. Transport is a
host-local UNIX-domain socket (0660, group=decnet); authz is the file
mode. Wire framing is a tiny verb-line + 4-byte-BE length + orjson body.
NATS-style wildcard topics (`*`, `>`). At-most-once, fire-and-forget —
DB stays the source of truth. `FakeBus` / `NullBus` for tests and the
disabled path. Cross-host federation is deferred to a future
`--bridge-tcp` mode; DEBT-030 is master-only and unblocked.
