fix(skills): add grill update marker example

src/skills/grill/SKILL.md

@@ -101,6 +101,11 @@ Use this format:
   Cause: Your answer made patent terms relevant to the license choice.
 ```
 
+```md
+~ [ ] Copyleft preference
+  Cause: The `src/skills/` exception leaves the rest of the monorepo under the root license.
+```
+
 Preserve agent judgment when the user reframes or invalidates a question.
 Show the resulting list change instead of following a rigid reframe algorithm.