feat: manage Handy preferences and startup declaratively

modules/capabilities/handy.nix

@@ -0,0 +1,46 @@
+{
+  flake.modules.homeManager.handy =
+    { config, pkgs, ... }:
+    let
+      settings = (pkgs.formats.json { }).generate "handy-settings.json" {
+        settings = {
+          settings_schema_version = 1;
+          selected_model = "handy-computer/nemotron-3.5-asr-streaming-0.6b-gguf/nemotron-3.5-asr-streaming-0.6b-Q8_0.gguf";
+          selected_language = "auto";
+          translate_to_english = false;
+          selected_microphone = null;
+          always_on_microphone = false;
+          push_to_talk = true;
+          paste_method = "ctrl_shift_v";
+          typing_tool = "wtype";
+          clipboard_handling = "dont_modify";
+          auto_submit = false;
+          overlay_style = "live";
+          overlay_position = "bottom";
+          post_process_enabled = false;
+          start_hidden = true;
+          autostart_enabled = false;
+          update_checks_enabled = false;
+          show_whats_new_on_update = false;
+          onboarding_completed = true;
+        };
+      };
+    in
+    {
+      home.packages = [ pkgs.handy ];
+
+      systemd.user.services.handy = {
+        Unit = {
+          Description = "Handy dictation";
+          PartOf = [ "graphical-session.target" ];
+          After = [ "graphical-session.target" ];
+        };
+        Install.WantedBy = [ "graphical-session.target" ];
+        Service = {
+          # Handy writes migrations and runtime preferences: restore the Nix baseline on start.
+          ExecStartPre = "${pkgs.coreutils}/bin/install -Dm600 ${settings} ${config.xdg.dataHome}/com.pais.handy/settings_store.json";
+          ExecStart = "${pkgs.handy}/bin/handy --start-hidden";
+        };
+      };
+    };
+}