The terminal's selectedCard comes from CardLookupResponse which uses
card_id field, but the JS was referencing selectedCard.id (undefined).
This caused all terminal transactions to fail with "LoyaltyCard with
identifier 'unknown' not found" instead of processing the transaction
or showing proper PIN validation errors.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>