hyprland: fix 0.55.0 option/dispatcher renames

Confirmed against the live 0.55.0 binary:
- misc:vfr → debug:vfr (release notes were right; my earlier probe was
  on the still-running 0.52.1 process, which is why I thought debug:vfr
  didn't exist)
- togglesplit isn't a top-level dispatcher anymore; it's a dwindle
  layoutmsg argument

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

settings/hyprland.nix

@@ -175,6 +175,10 @@
             # below; without that, focus jumps drag the cursor with them.
             focus_on_activate = false;
             vrr = 2; # always on — should engage at the 180 Hz EDID mode
+          };
+
+          # vfr moved from misc: to debug: in 0.55.0
+          debug = {
             vfr = false; # keep compositor ticking, don't idle between frames
           };
 
@@ -190,7 +194,7 @@
             "$mod, V, togglefloating"
             "$mod, F, fullscreen, 0"
             "$mod, P, pseudo"
-            "$mod, S, togglesplit"
+            "$mod, S, layoutmsg, togglesplit"
 
 
             # Focus