nixos: add quickshell/waybar/taffybar modules

- Switch taffybar input to the local submodule
- Add caelestia quickshell (home-manager module)
- Make waybar/taffybar mutually exclusive, defaulting based on xmonad
- Move tray ordering and status notifier watcher config into the right modules

nixos/quickshell.nix

@@ -0,0 +1,21 @@
+{ config, lib, makeEnable, inputs, ... }:
+makeEnable config "myModules.quickshell" false {
+  home-manager.sharedModules = [
+    inputs.caelestia-shell.homeManagerModules.default
+    ({ lib, nixos, ... }:
+      let
+        hyprlandEnabled = lib.attrByPath ["myModules" "hyprland" "enable"] false nixos.config;
+      in
+      {
+        programs.caelestia = {
+          enable = true;
+          cli.enable = true;
+          systemd.target = lib.mkDefault (
+            if hyprlandEnabled
+            then "wayland-session@Hyprland.target"
+            else "graphical-session.target"
+          );
+        };
+      })
+  ];
+}