Summary

The OpenAPI schema does not document the application/problem+json response format introduced in #464. Clients relying on the OpenAPI spec to discover the content negotiation feature will not know it exists.

Context

PR #464 (RFC 9457 Phase 2) added content negotiation: clients sending Accept: application/problem+json receive bare RFC 9457 ProblemDetail responses instead of the ApiResponse envelope. However, the OpenAPI schema generation (scripts/export_openapi.py) was not updated to reflect this, since content negotiation happens in exception handlers (not in controller return types) and Litestar's auto-generation does not discover it.

Scope

• Add ProblemDetail as an alternative error response schema in the OpenAPI spec
• Document the Accept: application/problem+json content negotiation behavior
• This likely requires Litestar app-level responses configuration or custom OpenAPI schema hooks
• Update scripts/export_openapi.py if needed

Acceptance Criteria

• OpenAPI schema includes ProblemDetail schema definition
• Error responses document both application/json (envelope) and application/problem+json (bare) content types
• Generated API reference page (Scalar UI) shows both response formats

Dependencies

• feat: implement RFC 9457 Phase 2 — application/problem+json and content negotiation #464 (RFC 9457 Phase 2 — done)