feat(frank-dragoon): put the endpoint on the app bridge so app containers can name it

An endpoint on podman's rootless default (pasta) has no address another
container can use, measured on 2026-10-19 from inside open-notebook:

  - 192.168.0.143:7770            connection refused (pasta forwards the
                                  published port in the host netns; no netavark
                                  DNAT exists for traffic arriving from a
                                  rootless bridge)
  - host.containers.internal:7770 200, but the alias resolves to 169.254.1.2 —
                                  link-local, which open-notebook's URL guard
                                  refuses to store
  - frank-dragoon-halogen:8731    name unknown: different netns
  - --network pasta --network dankclaw_default
                                  "cannot set multiple networks without bridge
                                  network mode" — pasta cannot be added to

So reaching the NPU endpoints from an app container means moving the container
onto dankclaw_default (FRANK_DRAGOON_NETWORK; empty keeps today's shape). This
is not an exposure change: the engine's unauthenticated token port binds the
container's own loopback (/proc/net/tcp: 127.0.0.1:8730 against 0.0.0.0:8731),
so only the API port becomes name-resolvable — the same trust the published
7770 already carries on the LAN. The deployer refuses a network that does not
exist rather than starting a unit that restart-loops on it.

Co-Authored-By: omp <omp@dankclaw>

scripts/serve-frank-dragoon.sh

@@ -187,6 +187,24 @@ if [ -n "$NPU_MODELS" ]; then
                -e HALOGEN_NPU_MODELS="$NPU_MODELS")
     echo "frank-dragoon: NPU lane armed: $NPU_MODELS on $DEV_ACCEL (fabric clock held)" >&2
 fi
+
+# Container network. Empty = podman's rootless default (`pasta`), which is a
+# private netns and CANNOT be joined by anything else: podman refuses a second
+# network while the primary is pasta ("cannot set multiple networks without
+# bridge network mode"), the endpoint's published port answers 200 on the host
+# and on the LAN but is REFUSED from a dankclaw_default container (measured
+# 2026-10-19), and `host.containers.internal:7770` answers 200 yet resolves to
+# 169.254.1.2 — link-local, which open-notebook's URL guard refuses to store.
+# So an endpoint on pasta has no address an app container can use; naming the
+# app bridge here is the only shape that lets open-notebook dial
+# http://frank-dragoon-halogen:8731 for the NPU endpoints. It does not widen
+# the surface: the engine's unauthenticated 8730 is bound to the container's
+# OWN loopback (/proc/net/tcp: 127.0.0.1:8730 vs 0.0.0.0:8731, checked the same
+# day), so only the API port is reachable by name.
+NET_ARGS=()
+if [ -n "${FRANK_DRAGOON_NETWORK:-}" ]; then
+    NET_ARGS=(--network "$FRANK_DRAGOON_NETWORK")
+fi
 # Host-RAM preflight — the engine's pin gate, checked BEFORE podman run.
 # The engine refuses to pin when MemAvailable is below the checkpoint plus
 # a 16 GiB floor: pinned pages cannot be swapped, and under the floor the
@@ -261,6 +279,7 @@ podman run --name "$FRANK_DRAGOON_CONTAINER" \
   ${HALOGEN_WEIGHTS_LOCK:+-e HALOGEN_WEIGHTS_LOCK="$HALOGEN_WEIGHTS_LOCK"} \
   -v "$FRANK_DRAGOON_MODEL_DIR:/models:ro" \
   -v "$FRANK_DRAGOON_MODEL_DIR/tokenizer:/tokenizer:ro" \
+  "${NET_ARGS[@]}" \
   "${NPU_ARGS[@]}" \
   "$FRANK_DRAGOON_IMAGE" \
   > "$LOG" 2>&1