Add initial implementation of design-an-interface skill and linking script

Co-authored-by: Copilot <copilot@github.com>

.claude-plugin/plugin.json

@@ -0,0 +1,6 @@
+{
+  "name": "mattpocock-skills",
+  "skills": [
+    "./skills/deprecated/design-an-interface"
+  ]
+}

scripts/link-skills.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Links all skills in the repository to ~/.claude/skills, so that
+# they can be used by the local Claude CLI.
+
+REPO="$(cd "$(dirname "$0")/.." && pwd)"
+DEST="$HOME/.claude/skills"
+mkdir -p "$DEST"
+
+find "$REPO/skills" -name SKILL.md -not -path '*/node_modules/*' -print0 |
+while IFS= read -r -d '' skill_md; do
+  src="$(dirname "$skill_md")"
+  name="$(basename "$src")"
+  target="$DEST/$name"
+
+  if [ -e "$target" ] && [ ! -L "$target" ]; then
+    rm -rf "$target"
+  fi
+
+  ln -sfn "$src" "$target"
+  echo "linked $name -> $src"
+done