Add reasoning.effort support for OpenAI gpt-realtime-2

### Feature Type Would make my life easier ### Feature Description OpenAI `gpt-realtime-2` supports configurable reasoning via `reasoning.effort`, but the Python OpenAI Realtime plugin does not seem to expose this option on `openai.realtime.RealtimeModel`. It would be useful to support something like: ```python from livekit.plugins import openai llm = openai.realtime.RealtimeModel( model="gpt-realtime-2", reasoning={"effort": "low"}, ) ``` ### Workarounds / Alternatives I don't think there is a clean workaround through the current Python `RealtimeModel` API. The only workaround I can see is patching the plugin locally to add `reasoning` to the session update payload. ### Additional Context OpenAI docs list these effort values: `minimal`, `low`, `medium`, `high`, `xhigh`. References: - https://developers.openai.com/api/docs/models/gpt-realtime-2 - https://developers.openai.com/api/docs/guides/realtime-models-prompting#set-reasoning-effort - Related JS issue: https://github.com/livekit/agents-js/issues/1433 - Related JS PR: https://github.com/livekit/agents-js/pull/1575