feat(desktop): nwg-displays writes niri outputs, kanshi dropped

The port swapped moonarch's wdisplays-persistent for the nixpkgs wdisplays,
which cannot save -- so the kanshi config stayed empty and its unit was
skipped on every boot. nwg-displays supports niri and writes the layout to
~/.config/niri/monitor.kdl, which niri applies itself.

niri prefers a home config and does not merge, so config.kdl is seeded with
an include of /etc/niri/config.kdl, like moonarch does for stasis.rune.

modules/services.nix

@@ -112,30 +112,6 @@ in
   # --- Firewall, replaces the ufw calls in post-install.sh ---
   networking.firewall.enable = true;
 
-  # --- Session services ---
-  #
-  # Rebuilt rather than copied: the upstream units reference /usr/bin/,
-  # which does not exist under Nix.
-
-  systemd.user.services.kanshi = {
-    description = "Dynamic display configuration";
-    partOf = [ "graphical-session.target" ];
-    after = [ "graphical-session.target" ];
-    wantedBy = [ "graphical-session.target" ];
-    # Without a config kanshi exits with a parse error and, with
-    # Restart=on-failure, spins. Monitor profiles are per machine.
-    unitConfig.ConditionPathExists = "%h/.config/kanshi/config";
-    # The config is read, never written, so ProtectSystem=strict is enough and
-    # no exception for %h is needed. Not exercised at runtime here: this host
-    # has no kanshi config, so the condition skips the unit.
-    serviceConfig = {
-      Type = "simple";
-      ExecStart = lib.getExe pkgs.kanshi;
-      Restart = "on-failure";
-      RestartSec = 3;
-    } // waylandClientHardening;
-  };
-
   # --- System services from defaults/etc/systemd/system/ ---
   #
   # Rebuilt rather than copied, same reason as the user units: the originals
@@ -166,6 +142,11 @@ in
     } // sysfsWriterHardening;
   };
 
+  # --- Session services ---
+  #
+  # Rebuilt rather than copied: the upstream units reference /usr/bin/,
+  # which does not exist under Nix.
+
   # The bar, launcher and every popout. A unit rather than a spawn-at-startup so
   # a crash does not leave the session without a bar until the next login.
   systemd.user.services.quickshell = {
@@ -262,7 +243,7 @@ in
   systemd.user.services.wlsunset = {
     description = "Wlsunset night light (blue light filter)";
     partOf = [ "graphical-session.target" ];
-    after = [ "graphical-session.target" "kanshi.service" ];
+    after = [ "graphical-session.target" ];
     wantedBy = [ ];
     serviceConfig = {
       Type = "simple";