home-manager/gui: Manage Codex with mutable settings

Pin Codex independently through `llm-agents.nix` and update unstable
home-manager for `programs.codex.mutableSettings`.

Declare the status line, including both usage windows, while preserving
imperative settings during activation.

home-manager/modules/gui/default.nix

@@ -1,4 +1,4 @@
-{ lib, pkgs', pkgs, config, ... }:
+{ lib, pkgs', pkgs, inputs, config, ... }:
 let
   inherit (lib) genAttrs mkIf mkMerge mkForce mapAttrs mkOptionDefault mkDefault optional;
   inherit (lib.my) mkOpt' mkBoolOpt';
@@ -187,6 +187,26 @@ in
             };
           };
 
+          codex = {
+            enable = true;
+            package = inputs.llm-agents.packages.${pkgs.stdenv.hostPlatform.system}.codex;
+            mutableSettings = true;
+            settings.tui = {
+              status_line = [
+                "model-with-reasoning"
+                "current-dir"
+                "five-hour-limit"
+                "weekly-limit"
+                "context-used"
+                "context-window-size"
+                "total-input-tokens"
+                "total-output-tokens"
+                "used-tokens"
+              ];
+              status_line_use_colors = true;
+            };
+          };
+
           claude-code = {
             enable = true;
             settings = {