hyprland: adapt to 0.55.0 breaking changes

0.55.0 keeps traditional config syntax — Lua is added, not required —
but two of our settings broke:
- misc:vfr moved to debug:vfr
- dwindle:pseudotile removed (it was a no-op anyway)

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

settings/hyprland.nix

@@ -147,7 +147,6 @@
 
           dwindle = {
             preserve_split = true;
-            pseudotile = true;
             # New windows split the focused container 50/50 — your usual
             # 2-way layout falls out of dwindle's defaults.
           };
@@ -160,6 +159,10 @@
             # 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 Hyprland 0.55.0
+          debug = {
             vfr = false; # keep compositor ticking, don't idle between frames
           };