feat: add hyprscratch scratchpad management with rule reapply fork

- Add hyprscratch from colonelpanic8/reapply-rules-on-toggle fork that
  reapplies size/position/float rules on every toggle (not just spawn)
- Configure 9 scratchpads: htop, volume, spotify, element, slack,
  transmission, dropdown, gmail, messages
- Use clean mode (hide on workspace change) and auto-dismiss (only
  dropdown persists)
- Fix pavucontrol class (org.pulseaudio.pavucontrol) and dropdown
  position (offset by taffybar height)
- Add kanshi-sni, dbus-menu, dbus-hslogger flake inputs and follows

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nixos/hyprland.nix

@@ -10,10 +10,77 @@ makeEnable config "myModules.hyprland" true {
     withUWSM = true;
   };
 
+  home-manager.sharedModules = [
+    inputs.hyprscratch.homeModules.default
+    {
+      services.kanshi = {
+        enable = true;
+        systemdTarget = "hyprland-session.target";
+      };
+
+      programs.hyprscratch = {
+        enable = true;
+        settings = {
+          daemon_options = "clean";
+          global_options = "";
+          global_rules = "float;size monitor_w*0.95 monitor_h*0.95;center";
+
+          htop = {
+            command = "alacritty --class htop-scratch --title htop -e htop";
+            class = "htop-scratch";
+          };
+
+          volume = {
+            command = "pavucontrol";
+            class = "org.pulseaudio.pavucontrol";
+          };
+
+          spotify = {
+            command = "spotify";
+            class = "spotify";
+          };
+
+          element = {
+            command = "element-desktop";
+            class = "Element";
+          };
+
+          slack = {
+            command = "slack";
+            class = "Slack";
+          };
+
+          transmission = {
+            command = "transmission-gtk";
+            class = "transmission-gtk";
+          };
+
+          dropdown = {
+            command = "ghostty --config-file=/home/imalison/.config/ghostty/dropdown";
+            class = "com.mitchellh.ghostty.dropdown";
+            options = "persist";
+            rules = "float;size monitor_w monitor_h*0.5;move 0 60;noborder;noshadow;animation slide";
+          };
+
+          gmail = {
+            command = "google-chrome-stable --new-window https://mail.google.com/mail/u/0/#inbox";
+            class = "google-chrome";
+            title = "Gmail";
+          };
+
+          messages = {
+            command = "google-chrome-stable --new-window https://messages.google.com/web/conversations";
+            class = "google-chrome";
+            title = "Messages";
+          };
+        };
+      };
+    }
+  ];
+
   # Hyprland-specific packages
   environment.systemPackages = with pkgs; [
     # Hyprland utilities
-    kanshi         # Monitor hotplug management
     hyprpaper      # Wallpaper
     hypridle       # Idle daemon
     hyprlock       # Screen locker