fix(waybar): carry tray-menu counter-rules in the bar stylesheet itself

The e8658fe cure (USER-priority gtk.css counter-rules) verified in a
plain GTK app but not in the real Waybar-hosted nm-applet menu: Waybar
adds its provider at GTK_STYLE_PROVIDER_PRIORITY_USER as well
(src/client.cpp), and in practice its rules win the tie against
~/.config/gtk-3.0/gtk.css on GTK 3.24 — reproduced by injecting the
bar stylesheet above USER priority: arrow, checkmark and separator all
vanish, matching the live menu exactly.

The only placement that wins at ANY provider priority is inside the
same stylesheet: after each '*' reset, restore the CSS-sized menu
nodes (menuitem arrow 16px, check/radio 14px, separator 1px line) and
give menus a text face instead of the bar's glyph font. Applied to
boreal + executive-slate waybar.css and waybar.nix generatedStyle;
stylix.nix comment corrected (its rules now cover ordinary GTK apps
only).

Ground truth checked over D-Bus first: nm-applet exports per-network
Wi-Fi icons as dbusmenu icon-data, and with gtk-menu-images=1 the
connected network's icon already renders in the live menu — the
remaining loss was arrows/checks/separators, all CSS-box nodes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

modules/home/stylix.nix

@@ -70,13 +70,13 @@ in
             }
             /* Submenu disclosure arrows need no icon remap: pan-end-symbolic
                resolves via Papirus-Dark's breeze-dark inheritance. The
-               "invisible arrow" bug is Waybar's process-wide stylesheet:
+               "invisible arrow" bug was Waybar's process-wide stylesheet:
                its `* { min-height: 0; }` reset also hits the SNI tray menus
-               Waybar hosts and collapses the arrow node. This file loads at
-               USER priority (~/.config/gtk-3.0/gtk.css), which outranks any
-               waybar.css (APPLICATION priority) — restore the arrow's box
-               here, exactly like the check/radio rule below already does
-               for the same collapse. */
+               Waybar hosts and collapses arrow/check nodes. NB: this file
+               CANNOT fix that — Waybar adds its provider at USER priority
+               too and wins the tie in practice (GTK 3.24, observed), so
+               every waybar.css carries its own menu counter-rules. The
+               rules here cover menus in ordinary GTK apps only. */
             menu menuitem arrow, .menu menuitem arrow, .context-menu menuitem arrow {
               min-width: 16px;
               min-height: 16px;