add emil-design-eng skill to install/update pipeline

- Download SKILL.md from emilkowalski/skill to skills-external/
- Symlink to ~/.claude/skills/ via link.sh
- install-plugins.sh step 9: curl download + symlink check
- update-all.sh step 8: re-fetch latest SKILL.md on update
- plugins.lock.json: add emil-design-eng entry
- .gitignore: ignore auto-created symlink in skills/

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

link.sh

@@ -46,6 +46,17 @@ else
   echo "⚠️  GStack submodule not found — run: git submodule update --init"
 fi
 
+if [ -d "$REPO/skills-external/emil-design-eng" ]; then
+  if [ -L "$CLAUDE/skills/emil-design-eng" ] && [ "$(readlink "$CLAUDE/skills/emil-design-eng")" = "$REPO/skills-external/emil-design-eng" ]; then
+    : # already correct
+  else
+    ln -sf "$REPO/skills-external/emil-design-eng" "$CLAUDE/skills/emil-design-eng"
+    CHANGED=$((CHANGED + 1))
+  fi
+else
+  echo "⚠️  emil-design-eng not found — run: make plugin"
+fi
+
 if [ "$CHANGED" -eq 0 ]; then
   echo "✅ All symlinks already up to date."
 else