refactor: derive host name solely from host directory name

utils/hosts.nix

@@ -1,3 +1,8 @@
+{ lib }:
+
+let
+  fs = import ./fs.nix { inherit lib; };
+in
 {
   hostMeta =
     hostDir:
@@ -5,4 +10,10 @@
       import (hostDir + "/meta.nix")
     else
       throw "meta.nix required in ${hostDir}";
+
+  adminHosts =
+    hostsPath:
+    builtins.filter (host: ((import (hostsPath + "/${host}/host.nix")).host.admin or false)) (
+      fs.dirNames hostsPath
+    );
 }