Implement order idempotency, reconciliation and failure-path tests #20

Outcome

Make duplicate delivery, timeout, and ambiguous broker responses safe and auditable in the demo environment.

Acceptance criteria

• Enforce a unique execution-intent/request identifier in application storage
• Use an explicit order state machine with valid transitions
• Reconcile ambiguous submissions before any retry
• Compare local intents and states with broker-observed orders
• Quarantine inconsistent states for manual review
• Test duplicate messages, lost responses, timeout, retry, partial fill, rejection, and process crash
• Produce an audit trail linking signal, risk decision, execution intent, and broker result
• Define the evidence required to close the demo milestone