chore(api): correct fine-tuning bounds and Realtime response reference (#3949)

## Summary

Corrects fine-tuning numeric bounds and Realtime client-secret response
alternatives in the Python API reference.

## Changes

- Use OpenAPI 3.1 numeric exclusive bounds for fine-tuning parameters.
- Identify realtime and transcription session alternatives in
client-secret responses.






## Why

The API reference used boolean `exclusiveMinimum` values, which are
invalid in OpenAPI 3.1. This corrects seven numeric lower bounds and
restores their existing `auto` defaults. Explicit discriminator mappings
also identify the existing `realtime` and `transcription` alternatives
in client-secret responses.

This is a reference-only correction: SDK source, public types,
dependencies, and request/response serialization are unchanged.

Source: [published OpenAPI
correction](https://github.com/openai/openai-openapi/commit/946e365dd69d52ccfe49fd0a9e565504aef517bd).

## Compatibility review

Reviewed head `add92714d353df33e1ee98a604800ce8b6e6d42d` against base
`4d1274681db7f34f671ff9e71adc1461d22a927b`.

- The complete tree diff contains only `.castiron.stats.yml` and
`api_reference/openapi.transformed.yml`. All SDK source, public
signatures, related model types, serializers, dependencies, and
package/build configuration are unchanged. Neither changed file is
consumed by the SDK runtime or enters its normal distributed code.
- Paired baseline/candidate Python client and model probes pass (183
cases per revision, identical results).
- The transformed reference passes 464 focused schema cases, including
actual enclosing requests/responses, lower/upper boundaries, `auto`,
omission, and both Realtime response variants.
- [Current-head
CI](https://github.com/openai/openai-python/actions/runs/35922654398)
passes.

Scope: this establishes no identified SDK-package compile-time or
runtime compatibility regression from this patch. Tools that directly
read the OpenAPI reference (validators, mock servers, or third-party
generators) can observe the corrected bounds, defaults, and explicit
mappings; those integrations are a separate compatibility surface. No
deployed-service test or package release is claimed.

Co-authored-by: markstuart-oai <323302876+markstuart-oai@users.noreply.github.com>