docs(api): describe response stream event unions

[jbeckwith-oai]

Summary

• Accurately describe stable and beta Responses streaming event unions.
• Refresh generated OpenAPI reference and Castiron provenance from the exact upstream source.
• Source: https://github.com/openai/openai/pull/1277036
• OpenAPI commit: bc61c5299f7f6fdd6061ccad0ac7e4ec0f659098

Validation

• Castiron local dry run and exact generated-candidate patch comparison.
• git diff --check and transformed OpenAPI reference hash verified.

[openai-sdks]

OkTest Summary

✅ 237/237 SDK tests passed in 16.268s for Java SDK PR #862.

Test results — 42 files

Test	Result	Time
tests/chat-completions-complex-body.test.ts	✅ Passed	222ms
tests/chat-completions-create.test.ts	✅ Passed	590ms
tests/chat-completions-stream.test.ts	✅ Passed	327ms
tests/files-content-binary.test.ts	✅ Passed	281ms
tests/files-create-multipart.test.ts	✅ Passed	271ms
tests/files-list-pagination.test.ts	✅ Passed	258ms
tests/initialize-config.test.ts	✅ Passed	168ms
tests/instance-isolation.test.ts	✅ Passed	300ms
tests/models-list.test.ts	✅ Passed	177ms
tests/responses-background-lifecycle.test.ts	✅ Passed	625ms
tests/responses-body-method-errors.test.ts	✅ Passed	477ms
tests/responses-cancel-timeout.test.ts	✅ Passed	202ms
tests/responses-cancel.test.ts	✅ Passed	302ms
tests/responses-compact-retries.test.ts	✅ Passed	494ms
tests/responses-compact.test.ts	✅ Passed	339ms
tests/responses-create-advanced-stream.test.ts	✅ Passed	257ms
tests/responses-create-advanced.test.ts	✅ Passed	1.41s
tests/responses-create-disconnect.test.ts	✅ Passed	1.155s
tests/responses-create-errors.test.ts	✅ Passed	330ms
tests/responses-create-malformed-api-responses.test.ts	✅ Passed	332ms
tests/responses-create-retries.test.ts	✅ Passed	268ms
tests/responses-create-stream-failures.test.ts	✅ Passed	251ms
tests/responses-create-stream-timeout.test.ts	✅ Passed	307ms
tests/responses-create-stream-wire.test.ts	✅ Passed	6.217s
tests/responses-create-stream.test.ts	✅ Passed	106ms
tests/responses-create-terminal-states.test.ts	✅ Passed	430ms
tests/responses-create-timeout.test.ts	✅ Passed	219ms
tests/responses-create.test.ts	✅ Passed	387ms
tests/responses-delete.test.ts	✅ Passed	230ms
tests/responses-input-items-errors.test.ts	✅ Passed	277ms
tests/responses-input-items-list.test.ts	✅ Passed	322ms
tests/responses-input-items-options.test.ts	✅ Passed	597ms
tests/responses-input-tokens-count-timeout.test.ts	✅ Passed	302ms
tests/responses-input-tokens-count.test.ts	✅ Passed	399ms
tests/responses-malformed-inputs.test.ts	✅ Passed	4.96s
tests/responses-not-found-errors.test.ts	✅ Passed	354ms
tests/responses-parse.test.ts	✅ Passed	710ms
tests/responses-retrieve-retries.test.ts	✅ Passed	322ms
tests/responses-retrieve.test.ts	✅ Passed	279ms
tests/responses-stored-method-errors.test.ts	✅ Passed	958ms
tests/retry-behavior.test.ts	✅ Passed	3.498s
tests/sdk-error-shape.test.ts	✅ Passed	439ms

View OkTest run #31752214456

_{SDK merge (8676f72d69b3) · head (45d5fc46ff92) · base (4936d0befb93) · OkTest (a845fa206fa4)}

[HAYDEN-OAI]

Reviewed the stable and beta streaming-event unions against the upstream OpenAPI change and generated model contracts. The corrected descriptions cover all response event variants without changing runtime behavior or public APIs.