feat(helpers): add zod realtime function helper

[HAYDEN-OAI]

Summary

• add zodRealtimeFunction() to openai/helpers/zod
• generate Realtime function tool definitions from Zod v3, Zod v4, and Zod v4 mini schemas
• omit strict, which is not part of the Realtime RealtimeFunctionTool shape
• add focused coverage for the generated schema and wire format

Motivation

Fixes #1809.

zodResponsesFunction() is close to what Realtime callers need, but it always emits strict: true. Realtime function tools use the flat { type, name, description?, parameters } shape and do not support that field, so raw Realtime users currently have to convert Zod schemas by hand.

Behavior

The new helper returns a regular Realtime function tool definition with type, name, optional description, and JSON Schema parameters. It reuses the existing Zod conversion path so behavior stays consistent across the helper family, including current Zod v3, v4, and v4 mini support.

The helper is intentionally definition-only. It does not attach callback or parser metadata because the raw Realtime client does not have a runTools()-style consumer; callers still parse function-call arguments with their original Zod schema.

Validation

• pnpm exec jest tests/helpers/zod.test.ts --runInBand
• pnpm exec prettier --check src/helpers/zod.ts tests/helpers/zod.test.ts
• git diff --check
• pnpm run lint

[openai-sdks]

OkTest Summary

❌ Failed for Node SDK PR #1996.

View OkTest run #29368639461

_{SDK merge (9f58df6ccd15) · head (c47069f89f26) · base (1cdc0196b434) · OkTest (cb7f0514ccd2)}

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Honor optional fields in Realtime schemas

When a Realtime tool has a normal optional parameter such as z.object({ limit: z.number().optional() }), this new helper still routes through the strict structured-output converters. Those converters reject .optional() without .nullable() and force nullable/defaulted fields into required, even though Realtime function tools only expose normal JSON Schema parameters and this helper intentionally omits the unsupported strict flag. As a result, valid non-strict Realtime function definitions cannot be produced, or are over-constrained, by the new helper.

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