hypr: switch default browser hotkey to Chrome

Firefox isn't installed; SUPER+W now launches google-chrome-stable,
and the opacity-override window rule matches Chrome's window class too.

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

.config/hypr/config/variables.lua

@@ -2,7 +2,7 @@
 
 TERMINAL     = "kitty"
 FILE_MANAGER = "dolphin"
-BROWSER      = "firefox"
+BROWSER      = "google-chrome-stable"
 EDITOR       = "gnome-text-editor --new-window"
 CALCULATOR   = "gnome-calculator"