berth updates

berth/ctrl/lib/estate.sh

@@ -123,3 +123,25 @@ except ValueError:
     sys.exit(2)
 ' "$1" "$2"
 }
+
+# The upstream a service actually resolves to, as "host:port".
+#
+# A PLACED service has no literal `upstream` field: ✖ B9 replaced langfuse's
+# hand-written `10.8.0.2:3000` with placement+peer+port, because being reached
+# by address on the overlay is ONE decision, not three properties. Everything
+# that asks "what does this service point at" must therefore resolve it the
+# same way, or it silently sees an empty string and skips the service — which
+# is exactly how vpn.sh's bindings invariant went quiet after B9 landed.
+#
+# usage: service_upstream <up> <placement> <peer> <port>
+service_upstream() {
+    local up="$1" placement="$2" peer="$3" port="$4"
+    case "$placement" in
+        local|instance)
+            local addr; addr="$(overlay_get estate "peers.${peer}.address")"
+            [ -z "$addr" ] && return 1
+            printf '%s:%s' "$addr" "$port"
+            ;;
+        *) printf '%s' "$up" ;;
+    esac
+}