fix: yazi fetcher group field, xfce package renames, enable nix-ld

Three quick known-issue fixes:

- yazi: 26.x made the fetcher `group` field required, so the git
  prepend_fetchers failed to parse and yazi fell back to presets. Add
  `group = "git"` to both entries (the git plugin's setup() only renders
  the linemode — the fetcher still needs registering here).
- file-manager: xfce.exo and the three Thunar plugins moved to top-level;
  use pkgs.xfce4-exo / pkgs.thunar-{archive-plugin,volman,media-tags-plugin}.
  Clears the eval-time deprecation warnings.
- nix-ld: enable programs.nix-ld distro-wide so foreign dynamically-linked
  binaries (downloaded tools, npx-fetched claude-code, language servers)
  run without patchelf.

Also drops the now-stale claude-code mention from the allowUnfree comment
(the ask module uses npx). nix flake check passes; xfce warnings gone.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/nixos/file-manager.nix

@@ -13,7 +13,7 @@ in
   config = lib.mkIf cfg.fileManager.enable {
     programs.thunar = {
       enable = lib.mkDefault true;
-      plugins = with pkgs.xfce; [
+      plugins = with pkgs; [
         thunar-archive-plugin    # create/extract archives from the context menu
         thunar-volman            # auto-manage removable drives/media
         thunar-media-tags-plugin # rename/inspect audio by tags
@@ -28,7 +28,7 @@ in
       ffmpegthumbnailer # video thumbnails (Thunar + yazi)
       libgsf            # ODF thumbnails
       poppler-utils     # PDF thumbnails / pdftoppm (yazi PDF preview too)
-      xfce.exo          # "Open Terminal Here" and default-app associations
+      xfce4-exo         # "Open Terminal Here" and default-app associations
       shared-mime-info  # MIME database
     ];
   };