refactor default apps and add walker

modules/capabilities/neovim/default.nix

@@ -4,6 +4,12 @@ let
   repoTheme = config.repo.theme.kanagawa;
 in
 {
+  flake.modules.homeManager.default-editor-neovim =
+    { pkgs, ... }:
+    {
+      xdg.mimeApps.defaultApplicationPackages = [ pkgs.neovim ];
+    };
+
   flake.modules.homeManager.neovim =
     {
       pkgs,