Adds CreateBody helper and 15 test runs (7 methods + 8 parametrized cases) covering happy path, 401 unauthenticated, malformed inner JSON, empty object, unknown card, not_craftable, would_exceed_max_copies, and insufficient_vials error paths for POST /card/create. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>