docs(swarm): drop known-limitation about master-side NIC mismatch

Agent now relocalizes master-built configs before dispatch (commit in
main repo: fix(swarm): relocalize master-built config on worker before
deploy). The wiki claimed this was a known limitation requiring
per-worker INI files; that workaround is no longer needed. Updated the
troubleshooting row to describe the new failure mode (worker can't
detect its own default route) instead of the old one.

SWARM-Mode.md

@@ -479,13 +479,6 @@ decnet swarm decommission --name <each-worker> --yes
 
 ## Known limitations
 
-- **`deploy --mode swarm` runs `get_host_ip(--interface)` on the master**
-  before dispatching to workers. This means `--interface` must name a NIC
-  that exists on the master. If your workers have different NIC names
-  (common in heterogeneous fleets), this fails. Workaround: use INI
-  per-worker configs that hardcode the right subnet, and call deploy
-  once per worker. A proper fix (defer network detection to the worker
-  agent) is tracked in `Roadmap-and-Known-Debt`.
 - **No web UI for swarm management yet.** CLI only. Dashboard integration
   is on the roadmap.
 - **No automatic discovery.** Workers don't broadcast; enrollment is
@@ -509,7 +502,7 @@ decnet swarm decommission --name <each-worker> --yes
 | `swarm list` shows `status=enrolled` indefinitely | `swarm check` has never been run, or agent is unreachable | Run `swarm check`; see row 1 if that fails |
 | Lines appear in `master.log` but not the dashboard | Ingester not running, or pointed at the wrong JSON path | `systemctl status decnet-ingester`, confirm `DECNET_INGEST_LOG_FILE` matches `listener --json-path` |
 | `deploy --mode swarm` fails with `No enrolled workers` | Exactly what it says | `swarm enroll` at least one worker first |
-| `deploy --mode swarm` fails on `get_host_ip` | The NIC name you passed doesn't exist on the master | See Known Limitations; use per-host INI files |
+| Worker returns 500 on `/deploy` with `ip addr show <nic>` error | The worker's agent is re-detecting its own NIC (this is the relocalize step) and can't find a usable interface | Run `ip route show default` on the worker — if empty, the default route is missing; fix the worker's networking before deploying |
 | Agent rejects master with `BAD_CERTIFICATE` | Master's own client cert (`~/.decnet/master/`) isn't in the worker's trust chain | Never happens if both sides were issued from the same CA. Check you didn't re-init the CA between `swarmctl` starts |
 
 If things are really broken and you want a clean slate on the master: