validate_order_status (scenarios/ecommerce.py)

Case study: E-commerce orders. Architectural pattern demonstrated: **compound state machine + reactions**. An order moves through cart -> placed -> paid -> shipped -> delivered, with refund inverting the state from delivered back to refunded. Each transition has invariants (place

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"""Case study: E-commerce orders.

Architectural pattern demonstrated: **compound state machine + reactions**.
An order moves through cart -> placed -> paid -> shipped -> delivered, with
refund inverting the state from delivered back to refunded. Each transition
has invariants (placed orders cannot be modified; only paid orders can ship).
The state-machine validator + reactions handle the bookkeeping; the handler
just describes the user intent (place / pay / ship / refund).

Object types: customer, product, order, order_item, audit_log
Key invariants:
  - order status follows: cart ->

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