hyprland: improve config reload

When using the previous approach I've always gotten errors that I can't
reload config on the .lock file that exists in /tmp when you run a
standard configured hyprland.

This commit improves this by using hyprctl to find instances to reload
instead.

We can remove the HYPRLAND_INSTANCE_SIGNATURE bogus assignment once
https://github.com/hyprwm/Hyprland/issues/4088 is resolved.

Co-authored-by: Carl Hjerpe <git@hjerpe.xyz>

modules/services/window-managers/hyprland.nix

@@ -243,11 +243,11 @@ in {
         + lib.optionalString (cfg.extraConfig != "") cfg.extraConfig;
 
       onChange = lib.mkIf (cfg.package != null) ''
-        (  # execute in subshell so that `shopt` won't affect other scripts
-          shopt -s nullglob  # so that nothing is done if /tmp/hypr/ does not exist or is empty
-          for instance in /tmp/hypr/*; do
-            HYPRLAND_INSTANCE_SIGNATURE=''${instance##*/} ${cfg.finalPackage}/bin/hyprctl reload config-only \
-              || true  # ignore dead instance(s)
+        ( # Execute in subshell so we don't poision environment with vars
+          # This var must be set for hyprctl to function, but the value doesn't matter.
+          export HYPRLAND_INSTANCE_SIGNATURE="bogus"
+          for i in $(${cfg.finalPackage}/bin/hyprctl instances -j | jq ".[].instance" -r); do
+            HYPRLAND_INSTANCE_SIGNATURE=$i ${cfg.finalPackage}/bin/hyprctl reload config-only
           done
         )
       '';