Fix Zen browser colors to follow active theme, not pywal cache

zen/userChrome.css read straight from ~/.cache/wal/colors.css, which
only updates on wallpaper pick and ignores static/shared theme
changes. Now generates zen.css from colors.toml via Omarchy's own
templating, same as waybar/alacritty/etc.

zen/userChrome.css

@@ -1,5 +1,7 @@
-/* Import Omarchy Pywal-generated system colors */
-@import url("file:///home/blob/.cache/wal/colors.css");
+/* Import the active Omarchy theme's colors (regenerated from colors.toml
+   on every theme change - static, dynamic, or shared - by
+   omarchy-theme-set-templates via omarchy/themed/zen.css.tpl) */
+@import url("file:///home/blob/.config/omarchy/current/theme/zen.css");
 
 :root {
     /* Map Omarchy colors to Zen variables */