fix: use dark GTK theme variant

profiles/contexts/desktop/theme/theme.nix

@@ -1,4 +1,4 @@
-# GTK and Qt theming — Dracula theme with matching icons and cursor.
+# GTK and Qt theming — system-wide dark Adwaita/libadwaita-compatible theme.
 {
   pkgs,
   config,
@@ -13,11 +13,14 @@
     enable = true;
     colorScheme = "dark";
     theme = {
-      name = "Adwaita";
+      # Must match a directory in pkgs.adw-gtk3/share/themes.
+      # "Adwaita" is not provided by this package and makes GTK4 import
+      # a missing CSS file; use the explicit dark variant instead.
+      name = "adw-gtk3-dark";
       package = pkgs.adw-gtk3;
     };
     iconTheme = {
-      name = "Papirus";
+      name = "Papirus-Dark";
       package = pkgs.papirus-icon-theme;
     };
     gtk4.theme = config.gtk.theme;