pinwheel: Use opensshs ssh-agent for SSH

As gnomes gcr-ssh-agent stalls RSA signing

hosts/pinwheel/modules/ssh/default.nix

@@ -3,10 +3,14 @@
   # Enable gnome-keyring at system level for PAM integration
   services.gnome.gnome-keyring.enable = true;
 
+  # Use openssh's own ssh-agent — gcr's ssh-agent stalls signing RSA keys.
+  services.gnome.gcr-ssh-agent.enable = false;
+  programs.ssh.startAgent = true;
+
   home-manager.users.alex = {
     services.gnome-keyring = {
       enable = true;
-      components = [ "secrets" "ssh" ];
+      components = [ "secrets" ];
     };
 
     programs.ssh = {