feat: port release-v2 experience improvements from #6582 (audited subset) (#6609)

packages/integrations/src/index.ts

@@ -102,3 +102,5 @@ export { downloadClientItemSchema } from "./interfaces/downloads/download-client
 
 // Helpers
 export { createIntegrationAsync } from "./base/creator";
+export { simulateResponseContractAsync } from "./base/response-contract";
+export type { ResponseContractFixture, ResponseContractParser } from "./base/response-contract";