Enable mutable Zed settings and add Codex ACP

Make Zed settings mutable, add codex-acp, and configure agent servers.

modules/home/zed/default.nix

@@ -13,6 +13,7 @@
     enable = true;
     package = pkgs.zed-editor;
     installRemoteServer = lib.mkIf config.zed-editor.remote-server.enable true;
+    mutableUserSettings = true;
   };
 
   imports = [

modules/home/zed/extra-packages.nix

@@ -12,5 +12,6 @@
     tailwindcss-language-server
     typescript-language-server
     omnisharp-roslyn
+    codex-acp
   ];
 }

modules/home/zed/user-settings/agent-servers.nix

@@ -0,0 +1,6 @@
+_: {
+  programs.zed-editor.userSettings.agent_servers = {
+    codex-acp.type = "registry";
+    opencode-v2.type = "registry";
+  };
+}

modules/home/zed/user-settings/default.nix

@@ -36,6 +36,7 @@ _: {
 
   imports = [
     ./agent.nix
+    ./agent-servers.nix
     ./language-models.nix
     ./languages.nix
     ./lsp.nix