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>

.claude/settings.local.json

@@ -276,7 +276,8 @@
       "Bash(nix-instantiate --parse modules/nixos/default.nix)",
       "Bash(cp /nix/store/f18ij42lmpg07fn1m29aplayakx7kqpz-splash-test.png/* preview-splash-built.png)",
       "Bash(cp /nix/store/f18ij42lmpg07fn1m29aplayakx7kqpz-splash-test.png preview-splash-built.png)",
-      "Bash(nix-instantiate --parse hosts/live.nix)"
+      "Bash(nix-instantiate --parse hosts/live.nix)",
+      "Bash(nix-instantiate --parse modules/home/stylix.nix)"
     ]
   }
 }