fix(desktop): correct dwindle keybinds and speed up the terminal

Two issues surfaced on the live neogaia session. Hyprland rejected two names
at load: the split toggle is a dwindle layout message reached through
layoutmsg, not a top-level dispatcher, and dwindle:pseudotile no longer exists
in this version. Bind Super+T via layoutmsg and drop the pseudotile option.

Ghostty also cold-started GTK on every launch. Configure it through
home-manager with gtk-single-instance so windows after the first open in the
existing process. Record the dispatcher/option version-drift trap in CLAUDE.md.

modules/desktop/hyprland/hyprland.nix

@@ -94,7 +94,6 @@ in
         };
 
         dwindle = {
-          pseudotile = true;
           preserve_split = true;
         };
 
@@ -121,7 +120,8 @@ in
 
           "$mod, Space, togglefloating,"
           "$mod, F, fullscreen,"
-          "$mod, T, togglesplit,"
+          # togglesplit is a dwindle layout message, reached through layoutmsg.
+          "$mod, T, layoutmsg, togglesplit"
           "$mod SHIFT, Q, killactive,"
           "$mod CTRL, Q, forcekillactive,"
         ]