Add codex 0.92.0 PR patch and fix deprecation warnings

- Add nixpkgs PR 483705 to bump codex from 0.89.0 to 0.92.0
- Disable overlay version overrides in favor of PR patches
- Replace deprecated pkgs.system with pkgs.stdenv.hostPlatform.system
- Replace deprecated xfce.thunar with thunar

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nixos/xmonad.nix

@@ -31,7 +31,7 @@ makeEnable config "myModules.xmonad" true  {
     # haskellPackages.gtk-sni-tray
     haskellPackages.status-notifier-item
     haskellPackages.dbus-hslogger
-    inputs.imalison-taffybar.defaultPackage."${pkgs.system}"
+    inputs.imalison-taffybar.defaultPackage."${pkgs.stdenv.hostPlatform.system}"
   ];
 
   home-manager.users = forEachUser {
@@ -43,7 +43,7 @@ makeEnable config "myModules.xmonad" true  {
 
     services.taffybar = {
       enable = true;
-      package = inputs.imalison-taffybar.defaultPackage."${pkgs.system}";
+      package = inputs.imalison-taffybar.defaultPackage."${pkgs.stdenv.hostPlatform.system}";
     };
 
     services.kdeconnect = {