fix(stylix): drive GTK4/Qt dark-light from the palette via color-scheme

Stylix set polarity and the GTK theme but not the XDG portal's
org.freedesktop.appearance color-scheme, which GTK4/libadwaita and Qt6
apps actually read to choose dark vs light — so a light theme could still
render those apps dark (and vice-versa).

Set dconf org/gnome/desktop/interface color-scheme to
prefer-light/prefer-dark from theme.mode in stylix.nix.
xdg-desktop-portal-gtk already ships and programs.dconf is on system-side,
so the portal exposes it to apps.

Also log two branding follow-ups from the legacy assets: fastfetch ASCII
logo (logo.txt) and the Nomarchy.ttf glyph for the Waybar menu button.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home/stylix.nix

@@ -86,5 +86,14 @@ in
         sizes.terminal = t.fonts.size;
       };
     };
+
+    # GTK4/libadwaita and Qt6 apps decide dark vs light from the XDG
+    # portal's color-scheme (org.freedesktop.appearance), which
+    # xdg-desktop-portal-gtk sources from this gsettings key. Stylix sets
+    # the GTK theme and `polarity` but not this, so a light theme still
+    # rendered libadwaita/Qt apps dark (and vice-versa). Drive it from the
+    # palette mode. (programs.dconf.enable is already on system-side.)
+    dconf.settings."org/gnome/desktop/interface".color-scheme =
+      if t.mode == "light" then "prefer-light" else "prefer-dark";
   };
 }