feat: nvim new configs

devshells/default.nix

@@ -35,15 +35,65 @@ let
     echo "Restart Claude Code and Codex to apply changes."
   '';
 
+  # Helper that builds the wrapped Neovim from the flake and runs it with repo-scoped XDG dirs
+  previewNvim = pkgs.writeShellScriptBin "preview-nvim" ''
+    set -euo pipefail
+
+    root="''${DOTFILES_ROOT:-$PWD}"
+    cache_base="$root/.cache"
+    nvim_cache="$cache_base/nvim-preview"
+    xdg_state="$cache_base/xdg-state"
+    xdg_data="$cache_base/xdg-data"
+    xdg_config="$root/modules/home/rsydn/programs"
+
+    mkdir -p "$nvim_cache" "$xdg_state" "$xdg_data"
+
+    attr="''${NVIM_ATTR:-}"
+    if [ "$#" -gt 0 ]; then
+      attr="$1"
+      shift
+    fi
+
+    if [ -z "$attr" ]; then
+      case "$(uname -s)" in
+        Darwin)
+          attr=".#darwinConfigurations.macbook-pro.config.home-manager.users.rasyidanakbar.programs.neovim.finalPackage"
+          ;;
+        Linux)
+          attr=".#nixosConfigurations.dev-vm.config.home-manager.users.rasyidanakbar.programs.neovim.finalPackage"
+          ;;
+        *)
+          echo "error: unsupported system; pass flake attribute as first argument or set NVIM_ATTR" >&2
+          exit 1
+          ;;
+      esac
+    fi
+
+    out_link="$nvim_cache/result"
+
+    echo "Building Neovim package: $attr"
+    XDG_CACHE_HOME="$nvim_cache" nix build "$attr" --out-link "$out_link"
+
+    echo "Launching Neovim..."
+    XDG_CACHE_HOME="$nvim_cache" \
+    XDG_STATE_HOME="$xdg_state" \
+    XDG_DATA_HOME="$xdg_data" \
+    XDG_CONFIG_HOME="$xdg_config" \
+    NVIM_APPNAME="nvim" \
+    "$out_link/bin/nvim" "$@"
+  '';
+
 in pkgs.mkShell {
   name = "default";
   packages = with pkgs; [
     git
+    nix
     nixfmt-classic
     uv
     python3
     mcpNixosWrapper
     installMcpConfigs
+    previewNvim
   ];
   shellHook = ''
     export DOTFILES_ROOT="$PWD"
@@ -63,5 +113,8 @@ in pkgs.mkShell {
     echo ""
     echo "To install MCP configs for Claude Code and Codex, run:"
     echo "  install-mcp-configs"
+    echo ""
+    echo "To preview the Neovim config without switching, run:"
+    echo "  preview-nvim [flakeAttr] [-- extra args]"
   '';
 }