ci: smoke test runs the container in file mode, surface its logs on failure

.gitea/workflows/gates.yml

@@ -347,18 +347,36 @@ jobs:
           # `-p 127.0.0.1::8080` takes an ephemeral host port instead of a
           # fixed 18080, which two concurrent runs on this daemon cannot both
           # bind. The actual port is read back with `docker port`.
+          #
+          # The command and the sysctl mirror deploy/docker/compose.yaml,
+          # because that is the invocation this gate exists to prove. The
+          # invocation is the sole configuration authority (milestone-20 ruling
+          # 1): the image's bare `run` grades the database, and a fresh
+          # /var/lib/nxdns volume holds no upstream, so it exits 2 with
+          # NoUsableUpstreams before it ever binds a port.
           net=$(docker inspect "$(hostname)" \
             -f '{{range $k, $v := .NetworkSettings.Networks}}{{$k}}{{end}}' \
             2>/dev/null || true)
           cid=$(docker create --name "$SMOKE_NAME" \
             ${net:+--network "$net"} \
             -p 127.0.0.1::8080 \
-            "$CI_IMAGE")
+            --sysctl net.ipv4.ip_unprivileged_port_start=0 \
+            "$CI_IMAGE" run --config=/etc/nxdns/config.zon)
           trap 'docker rm -f "$SMOKE_NAME" >/dev/null 2>&1 || true' EXIT
           docker cp etc-nxdns/config.zon "$SMOKE_NAME:/etc/nxdns/config.zon"
           docker start "$SMOKE_NAME"
 
-          hostport=$(docker port "$SMOKE_NAME" 8080/tcp 2>/dev/null | head -1 | awk -F: '{ print $NF }')
+          # Before anything that assumes a live container. `docker port` fails
+          # on one that already exited, and under `set -e` that failure is the
+          # whole diagnosis the log gets — the container's own stderr never
+          # reaches CI.
+          if [ "$(docker inspect -f '{{.State.Running}}' "$cid")" != "true" ]; then
+            echo "container exited during startup"
+            docker logs "$cid" || true
+            exit 1
+          fi
+
+          hostport=$(docker port "$SMOKE_NAME" 8080/tcp | head -1 | awk -F: '{ print $NF }')
           ip=$(docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' "$cid")
           echo "published host port: ${hostport:-none}, container ip: ${ip:-none}"
           healthy=""