Enable OpenCode and add its configuration

Enable the OpenCode service on both desktop and laptop hosts.
Import the opencode module into the home configuration and provide
settings, plugins, extra packages, and skill definitions for full
functionality.

modules/home/codex/default.nix

@@ -10,6 +10,9 @@
     enable = true;
     package = pkgs.codex;
     mutableSettings = true;
+    # skills = {
+    #   beads = "${pkgs.beads.src}/plugins/beads/skills/beads";
+    # };
   };
 
   imports = [