🐛 fix(playbook): import Optional for cli compatibility

restore the missing typing.Optional import in scripts/playbook.py
so older python runtimes can import the CLI module successfully.

add a regression test for typing annotation imports and register it
in the tests README.

scripts/playbook.py

@@ -6,6 +6,7 @@ from pathlib import Path
 from shutil import copy2, copytree, rmtree, which
 import subprocess
 import importlib.util
+from typing import Optional
 
 try:
     import tomllib