fix

modules/features/identity/ssh-default-key.nix

@@ -0,0 +1,31 @@
+{
+  pkgs,
+  lib,
+  config,
+  ...
+}:
+let
+  cfg = config.my.features.identity.sshDefaultKey;
+in
+{
+  options.my.features.identity.sshDefaultKey = {
+    enable = lib.mkEnableOption "Generate default SSH key (ed25519)";
+  };
+
+  config.home-manager.sharedModules = [
+    {
+      config = lib.mkIf cfg.enable {
+        home.activation.generateSshKey = lib.hm.dag.entryAfter [ "writeBoundary" ] ''
+          key="$HOME/.ssh/id_ed25519"
+          if [ ! -f "$key" ]; then
+            umask 077
+            mkdir -p "$HOME/.ssh"
+            ${pkgs.openssh}/bin/ssh-keygen -t ed25519 -N "" -f "$key" \
+              -C "moons@$(${pkgs.hostname}/bin/hostname || echo host)"
+            echo "Generated SSH key at $key"
+          fi
+        '';
+      };
+    }
+  ];
+}