docs(desktop): document Umbriel compositor configuration

docs/chezmoi/data.mdx

@@ -41,6 +41,7 @@ One manifest per platform, plus a `shared` block. Any edit to the file changes t
 | pacman | `niri`, `noctalia`, `xwayland-satellite`, `polkit-gnome`, `uwsm`, `xdg-user-dirs`; Wayland utilities `wl-clipboard`, `cliphist`, `wtype`, `ydotool`, `grim`, `slurp`, `hyprpicker`, `pamixer`, `brightnessctl`, `libnotify`; apps `nautilus`, `imv`, `mpv`, `evince`, `chromium`, `obsidian`; strata runtime deps `bubblewrap`, `desktop-file-utils`, `fontconfig`, `gstreamer`, `gst-libav`, `gst-plugins-base`, `gst-plugins-good`, `gtk4`, `gtksourceview5`, `gvfs`, `poppler-glib`, `xdg-utils` |
 | AUR (or a sync repo with the same name) | `vicinae-bin`, `tldraw-offline-bin`; desktop apps `beeper-bin`, `fastmail`, `1password`, `brave-origin-bin`, `claude-desktop`, `spotify` |
 | `[omarchy]` repo (`packages.arch.desktop.omarchy`, only when `pacman-conf -l` lists that repo) | `herdr`, `flea`, `voxtype-bin`, `xdg-terminal-exec`, `hyprland-preview-share-picker` |
+| `[cachyos]` repo (`packages.arch.desktop.cachyos`, only when `pacman-conf -l` lists that repo) | `umbriel` (the AUR `umbriel` is a placeholder and `umbriel-git` conflicts with the repo build) |
 
 Hyprland, Waybar and the `omarchy-*` commands come with the Omarchy install and are not declared. `niri-dynamic-workspaces` (niri startup) has no package; install it by hand. strata (the folder handler) has no package either; [15-tools](/chezmoi/scripts#15-tools) runs its installer.