✓ help blocks confirm
  keys: enter -> ? -> y -> escape -> y -> q
  actions: Push(confirm) -> Push(help) -> Stay -> Pop(None) -> Pop('api-gateway') -> Quit
  stack: [base(cursor=0:api-gateway)]

✓ cancel confirm
  keys: j -> enter -> n -> q
  actions: Stay -> Push(confirm) -> Pop(None) -> Quit
  stack: [base(cursor=1:auth-service)]

✓ base never pops
  keys: x -> q
  actions: Pop('base-pop') -> Quit
  stack: [base(cursor=0:api-gateway)]

✓ layers demo: 3 scenarios
actions: Stay=2 Push=3 Pop=4 Quit=3
invariants: base_never_pops ✓
