feat(home/pi): add hallmark design skill

Package Hallmark 1.1.0 for discovery through Pi’s conventional skills directory.

Assisted-by: pi (openai-codex/gpt-5.6-sol)

home/gabriel/features/pi/packages/default.nix

@@ -1,5 +1,6 @@
 {
   imports = [
+    ./hallmark.nix
     ./pi-claude-bridge.nix
     ./pi-codex-image-gen.nix
     ./pi-llama-cpp.nix

home/gabriel/features/pi/packages/hallmark.nix

@@ -0,0 +1,15 @@
+{pkgs, ...}: let
+  hallmark = pkgs.buildPiPackage {
+    pname = "hallmark";
+    version = "1.1.0";
+    src = pkgs.fetchFromGitHub {
+      owner = "Nutlope";
+      repo = "hallmark";
+      rev = "aeb42fb354ff4efa36ab475773a082315a3af2ce";
+      hash = "sha256-+yPIG1XdI6hhyOH48rd20+YlFrA9Gr416tPt1OoxfwQ=";
+    };
+    dontNpmInstall = true;
+  };
+in {
+  programs.pi-coding-agent.settings.packages = [hallmark];
+}