feat(keychain): use keychain for ssh agent

flake.nix

@@ -255,6 +255,7 @@
                   vim
                   gpg
                   ssh
+                  keychain
 
                   # Terminal
                   starship

users/profiles/gpg.nix

@@ -6,7 +6,6 @@
 
   services.gpg-agent = {
     enable = true;
-    enableSshSupport = true;
     pinentryFlavor = (if main.services.xserver.enable then "qt" else "curses");
     extraConfig = ''
       allow-emacs-pinentry

users/profiles/keychain.nix

@@ -0,0 +1,9 @@
+{ config, pkgs, ... }:
+{
+  programs.keychain = {
+    enable = true;
+    extraFlags = [ "--quiet" "--dir ${config.xdg.configHome}/keychain" ];
+
+    keys = [ "id_ed25519" ];
+  };
+}