add zsh module

modules/system/programs/default.nix

@@ -0,0 +1,7 @@
+{ ... }: {
+  flake.nixosModules.programs = {
+    programs.niri.enable = true;
+    programs.steam.enable = true;
+    programs.direnv.enable = true;
+  };
+}

modules/system/programs/zsh.nix

@@ -0,0 +1,19 @@
+{ ... }: {
+  flake.nixosModules.zsh = {
+    programs.zsh = {
+      enable = true;
+      enableCompletion = true;
+      autosuggestions.enable = true;
+      syntaxHighlighting.enable = true;
+      ohMyZsh = {
+        enable = true;
+        theme = "gentoo";
+      };
+      shellInit = ''
+        export SSH_AUTH_SOCK="$XDG_RUNTIME_DIR/rbw/ssh-agent-socket"
+        eval "$(devenv hook zsh)"
+      '';
+    };
+    system.userActivationScripts.zshrc = "touch .zshrc";
+  };
+}