refactor(nix): use executable helpers for desktop commands

configs/nixos/modules/desktop/apps/ghostty.nix

@@ -16,7 +16,7 @@ in
       keys = "SUPER + Return";
       action = {
         kind = "exec";
-        command = "${pkgs.ghostty}/bin/ghostty";
+        command = lib.getExe pkgs.ghostty;
       };
     };
 

configs/nixos/modules/desktop/session/hyprland/hypridle.nix

@@ -21,10 +21,10 @@
         general = {
           # The guard drops the call when a locker is already up, so no idle
           # trigger stacks a second hyprlock over the first.
-          lock_cmd = "${pkgs.procps}/bin/pidof hyprlock || ${pkgs.hyprlock}/bin/hyprlock";
+          lock_cmd = "${lib.getExe' pkgs.procps "pidof"} hyprlock || ${lib.getExe pkgs.hyprlock}";
           before_sleep_cmd = "loginctl lock-session";
           # Waking pokes the compositor in case firmware leaves displays dark.
-          after_sleep_cmd = "${config.programs.hyprland.package}/bin/hyprctl dispatch 'hl.dsp.dpms({ action = \"enable\" })'";
+          after_sleep_cmd = "${lib.getExe' config.programs.hyprland.package "hyprctl"} dispatch 'hl.dsp.dpms({ action = \"enable\" })'";
         };
 
         listener = [

configs/nixos/modules/desktop/session/hyprland/hyprlock.nix

@@ -13,28 +13,28 @@ let
     unit=lockscreen-idle-inhibit.service
 
     refresh_waybar() {
-      ${pkgs.procps}/bin/pkill -RTMIN+9 waybar >/dev/null 2>&1 || true
+      ${lib.getExe' pkgs.procps "pkill"} -RTMIN+9 waybar >/dev/null 2>&1 || true
     }
 
-    if ${pkgs.systemd}/bin/systemctl --user is-active --quiet "$unit"; then
-      ${pkgs.systemd}/bin/systemctl --user stop "$unit"
+    if ${lib.getExe' pkgs.systemd "systemctl"} --user is-active --quiet "$unit"; then
+      ${lib.getExe' pkgs.systemd "systemctl"} --user stop "$unit"
       refresh_waybar
-      ${pkgs.swayosd}/bin/swayosd-client --custom-message "${sleepIcon}"
+      ${lib.getExe' pkgs.swayosd "swayosd-client"} --custom-message "${sleepIcon}"
       exit 0
     fi
 
-    if ${pkgs.systemd}/bin/systemd-run \
+    if ${lib.getExe' pkgs.systemd "systemd-run"} \
       --user \
       --collect \
       --unit=lockscreen-idle-inhibit \
       --description="Disable idle-triggered screen locking" \
-      ${pkgs.systemd}/bin/systemd-inhibit \
+      ${lib.getExe' pkgs.systemd "systemd-inhibit"} \
       --what=idle \
       --who=lockscreen-hotkey \
       --why="lock screen disabled by hotkey" \
-      ${pkgs.coreutils}/bin/sleep infinity >/dev/null; then
+      ${lib.getExe' pkgs.coreutils "sleep"} infinity >/dev/null; then
       refresh_waybar
-      ${pkgs.swayosd}/bin/swayosd-client --custom-message "${sleepOffIcon}"
+      ${lib.getExe' pkgs.swayosd "swayosd-client"} --custom-message "${sleepOffIcon}"
     fi
   '';
 in
@@ -85,7 +85,7 @@ in
           kind = "exec";
           # The guard drops the call when a locker is already up, so no manual
           # trigger stacks a second hyprlock over the first.
-          command = "${pkgs.procps}/bin/pidof hyprlock || ${pkgs.hyprlock}/bin/hyprlock";
+          command = "${lib.getExe' pkgs.procps "pidof"} hyprlock || ${lib.getExe pkgs.hyprlock}";
         };
       };
 

src/skills/style/nix/rules/general.md

@@ -21,3 +21,32 @@ Do not call `lib.removeSuffix ".nix"` outside the utility definition.
 ### Rationale
 
 The utility centralizes Nix file-name normalization.
+
+## Use executable helpers for package commands
+
+### Rule
+
+Use `lib.getExe` for a package's main executable.
+Use `lib.getExe'` for a package's non-main executable.
+Do not build executable paths with `"${pkg}/bin/name"` when an executable helper names the target.
+Use `lib.getExe' config.programs.<name>.package "tool"` when a command follows a configured package option.
+
+### Rationale
+
+Executable helpers select the package output that contains binaries.
+They make package ownership explicit.
+`lib.getExe'` prevents calls to a package's main executable when code needs another tool.
+
+## Prefer NixOS package ownership for commands
+
+### Rule
+
+Use `pkgs.<name>` for Home Manager tools.
+Use `config.programs.<name>.package` when a NixOS module owns the package selection.
+Do not read `config.home-manager.users.<user>.programs.<name>.package` for command paths.
+
+### Rationale
+
+Home Manager uses the NixOS package set in this repository.
+`pkgs.<name>` avoids dependency paths through the user tree under Home Manager.
+Configured NixOS package options preserve package selection when a module owns the tool.