Add Omarchy-style Hyprland desktop for straylight

Ports the classic dotfiles Omarchy setup to a no-home-manager NixOS
system module (configs/omarchy.nix), scoped to straylight only so the
other desktop hosts keep i3.

- Hyprland (programs.hyprland) becomes the default lightdm session; i3
  stays enabled and selectable as a fallback.
- Omarchy config layout under ~/.config/{hypr,waybar,rofi,wlogout,
  swayosd,alacritty} symlinked from the store; mutable theme/wallpaper
  state in ~/.config/omarchy/current.
- omarchy-dots generates 8 themes (hyprland/hyprlock/waybar/rofi/
  swayosd/wlogout/alacritty/mako colour files) from each theme's
  palette, with wallpapers fetched from the Omarchy v3.8.4 tag.
- Helper scripts: omarchy-theme-set/bg-next/bg-set/apply, omarchy-menu
  (rofi power/theme/background menus), waybar toggle, screenshot, lock.
- Shared desktop modules (desktop.nix / desktop-light.nix) untouched.

configs/omarchy/hypr/input.conf

@@ -0,0 +1,28 @@
+# Input devices. kb_options matches Kyle's existing i3 xkb settings
+# (ctrl:swapcaps + right-alt compose) so muscle memory carries over.
+
+input {
+  kb_layout = us
+  kb_options = ctrl:swapcaps,compose:ralt
+
+  repeat_rate = 40
+  repeat_delay = 250
+
+  numlock_by_default = true
+
+  follow_mouse = 1
+  sensitivity = 0
+
+  touchpad {
+    clickfinger_behavior = true
+    scroll_factor = 0.4
+    natural_scroll = false
+  }
+}
+
+# Scroll nicely in the terminal
+windowrule = match:class (Alacritty|kitty|foot|com.mitchellh.ghostty), scroll_touchpad 1.5
+
+gestures {
+  workspace_swipe = false
+}