bao: mkRemovedOptionModule for matrixCtlHiveName

A plain removal breaks any out-of-tree host config that still sets the
option: eval fails with "option does not exist" and no pointer to what
replaced it. mkRemovedOptionModule gives a clear evaluation error instead.

nix/host-modules/swarm-bao.nix

@@ -1190,6 +1190,14 @@ let
   privateNetwork = false;
 in
 {
+  imports = [
+    (lib.mkRemovedOptionModule [ "services" "hyperhive" "deploy" "bao" "matrixCtlHiveName" ] ''
+      swarm-controller is the only minter of the per-hive matrix sender token,
+      and this option named a write grant matrix-ctl no longer holds. Delete
+      this setting.
+    '')
+  ];
+
   # One service, two namespaces, and the split decides who may set what.
   #
   # `deploy.bao.*` is mostly what the host RUNNING the store decides: whether