feat: Add host sydpc

My, this is a lot TwT.  Much work was batched as part of the transition from
guix-rebound to nixos-testbed/sydpc.

- Discord/Vesktop module & config.
- Syncthing setup.
- Assorted Emacs changes.
- Waybar config.
- Niri config.
- Steam config.
- Some MPD.
- Stylix config.
- Files/Impermanence things.
- Enable Ghostty.
- God knows what else.

modules/home/users/crumb/emacs/modules/lang/syd-lang-kdl.el

@@ -0,0 +1,9 @@
+;;; syd-lang-kdl.el -*- lexical-binding: t; -*-
+
+(use-package kdl-ts-mode
+  :mode "\\.kdl\\'"
+  :straight (:type git
+             :host github
+             :repo "dataphract/kdl-ts-mode"))
+
+(provide 'syd-lang-kdl)