force each container's unit configs in the checks about it

nix/module-eval/bao-matrix-reader.nix

@@ -21,6 +21,7 @@ let
     hive
     hiveWithController
     runGroup
+    forceServiceConfigs
     ;
 
   # The store and a service that reads from it, versus the store alone. The
@@ -61,6 +62,12 @@ let
   };
 
   cases = [
+    {
+      # Every unit in the container merges without a priority collision, not
+      # only the keys the cases here read.
+      name = "the homeserver's container units merge without a priority collision";
+      ok = forceServiceConfigs baoWithMatrix.containers.hive-matrix.config;
+    }
     {
       # A hive holds no shared queue credential for its agents, wherever the
       # store runs. The control: hive-c0re renders on both hosts.