fix(waybar): drop the bar to the bottom layer so fullscreen covers it

On Hyprland the `top` layer renders above every window, including a real
fullscreen surface — so a browser video gone fullscreen sat *under* the
bar (BACKLOG item 30). Move the bar to `layer: bottom` in the generated
waybar.nix and all four whole-swap jsoncs (parity rule); the exclusive
zone still reserves its space in normal tiling, but a fullscreen window
now covers it. Rationale comment kept in waybar.nix; data jsoncs left
comment-free (they carry none).

Verified: V0 (nix flake check --no-build, green) + V1
(homeConfigurations.nomarchy.activationPackage builds; built
.config/waybar/config shows "layer": "bottom"). V3 queued in
HARDWARE-QUEUE (fullscreen covers bar + returns on exit; floating-overlap
trade-off).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home/waybar.nix

@@ -119,7 +119,12 @@ let
     (lib.mapAttrsToList (name: value: "@define-color ${name} ${value};") t.colors);
 
   generatedSettings = {
-    layer = "top";
+    # `bottom`, not `top`: on Hyprland the `top` layer renders above every
+    # window — so a real fullscreen surface (a browser video gone
+    # fullscreen) sits *under* the bar. On `bottom` the fullscreen window
+    # covers the bar, while the exclusive zone still reserves its space in
+    # normal tiling. Keep in sync with the whole-swap jsoncs (parity rule).
+    layer = "bottom";
     position = "top";
     height = 34;
     margin-top = t.ui.gapsOut;