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/gitea-runner.nix

@@ -40,7 +40,7 @@ makeEnable config "myModules.gitea-runner" false {
       url = "https://dev.railbird.ai";
       tokenFile = config.age.secrets.gitea-runner-token.path;
       labels = [
-        "nixos-${pkgs.system}:host"
+        "nixos-${pkgs.stdenv.hostPlatform.system}:host"
         "nix:docker://localhost:5921/nix-runner"
       ];
     };