- Add scripts/generate-openapi.ts to generate OpenAPI 3.0 spec from SDK types
- Add scripts/validate-openapi.ts to validate spec against SDK endpoints
- Add .spectral.yaml for OpenAPI linting configuration
- Add npm scripts: generate:openapi, validate:openapi, lint:openapi
- Add documentation in scripts/README.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

- Automatically adds Idempotency-Key header parameter to all POST, PUT, PATCH operations
- Ensures generated clients expose idempotency as a first-class feature
- Updates README to document idempotency support
- Validates against SDK implementation in src/resource.ts

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

- Add Prefer header (respond-async/respond-sync) to POST operations
- Add enum values to expand query parameters for Entity and Account
- Document response headers: idempotency tracking and pagination
- Update README with documentation for new features

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>