BOS: bake the bread-theme CLI and generate the shared stylesheet at login

- Add bread-theme to the binaries baked into /etc/skel from bakery state.
- Run `bread-theme generate` first in the Hyprland autostart so the shared
  GUI stylesheet ($XDG_RUNTIME_DIR/bread/theme.css) exists before breadbar /
  breadbox / bos-settings paint (they also live-reload it on change).

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

iso/airootfs/etc/skel/.config/hypr/hyprland.lua

@@ -188,6 +188,9 @@ hl.bind("XF86AudioPlay",         hl.dsp.exec_cmd("playerctl play-pause"),
 -- ---------------------------------------------------------------------------
 hl.on("hyprland.start", function()
     local startup = {
+        -- Generate the shared bread GUI stylesheet first, so breadbar/breadbox/
+        -- bos-settings load it on start (they also live-reload if it changes).
+        "bread-theme generate",
         -- Global dark theme: GTK4/libadwaita + GTK3 theme + icon + cursor.
         "gsettings set org.gnome.desktop.interface color-scheme prefer-dark",
         "gsettings set org.gnome.desktop.interface gtk-theme Adwaita-dark",