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/early-init.el

@@ -10,8 +10,11 @@
 (setq use-package-compute-statistics t)
 
 (setq gc-cons-threshold
-      ;; (6 gibibytes)
-      (* 6 (expt 1024 3)))
+      ;; (8 gibibytes)
+      (* 8 (expt 1024 3)))
+
+(set-frame-parameter nil 'drag-with-header-line t)
+(set-frame-parameter nil 'undecorated t)
 
 ;; By default, Emacs will cache compilation artifacts in my personal config
 ;; directory — I'm not keen on that!  Redirect it to a dedicated cache directory.