fix(waybar): scope the universal CSS reset to the bar — un-hides tray submenu arrows

BACKLOG #90 root-caused: the arrows were never missing from the icon
theme — Papirus-Dark resolves pan-end-symbolic through its breeze-dark
inheritance (breeze ships inside the nixpkgs papirus output). The real
culprit: Waybar loads its stylesheet screen-wide at application
priority, so the tray menus it hosts for SNI apps (nm-applet & co)
inherit the bar's '* { min-height: 0; }', which out-prioritizes
adw-gtk3's 16px min-height on the menuitem arrow node and collapses
the submenu arrow to zero height. Property bisect confirmed
min-height:0 alone reproduces; the font/border resets don't.

- boreal + executive-slate waybar.css, waybar.nix generatedStyle:
  '*' block scoped to 'window#waybar, window#waybar *'; tooltip rules
  restate the font (tooltips are separate toplevels outside the scope).
- stylix.nix: drop the go-next-symbolic remap — a workaround for the
  misdiagnosis; native pan-end-symbolic resolves fine.
- BACKLOG #90 deleted; JOURNAL entry records the method (live GTK3
  repro + grim screenshots + CSS property bisect, V3 on TuringMachine).

V3 pending: human click on the real nm-applet tray icon post-switch.

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

modules/home/stylix.nix

@@ -36,10 +36,6 @@ let
     base0F = hex c.bad;      # brown/deprecated
   };
 
-  # Submenu disclosure arrows: GTK/Adwaita expect pan-end-symbolic,
-  # but Papirus doesn't ship it. Instead of complex CSS overrides and
-  # bundled SVGs, we map the GTK CSS to use go-next-symbolic which
-  # DOES exist in Papirus.
 in
 {
   config = lib.mkIf cfg.stylix.enable {
@@ -72,13 +68,11 @@ in
             menu menuitem:disabled, .menu menuitem:disabled {
               color: #${base16.base03};
             }
-            /* Submenu disclosure arrows: map missing pan-end-symbolic to existing go-next-symbolic. */
-            menu menuitem arrow:dir(ltr), .menu menuitem arrow:dir(ltr), .context-menu menuitem arrow:dir(ltr) {
-              -gtk-icon-source: -gtk-icontheme("go-next-symbolic");
-            }
-            menu menuitem arrow:dir(rtl), .menu menuitem arrow:dir(rtl), .context-menu menuitem arrow:dir(rtl) {
-              -gtk-icon-source: -gtk-icontheme("go-previous-symbolic");
-            }
+            /* Submenu disclosure arrows need no icon remap: pan-end-symbolic
+               resolves via Papirus-Dark's breeze-dark inheritance. The
+               "invisible arrow" bug was Waybar's stylesheet leaking
+               min-height:0 into the tray menus it hosts — fixed by scoping
+               the `*` block in every waybar.css to window#waybar. */
             check, radio {
               min-width: 14px;
               min-height: 14px;