fix(openai): preserve non-instruction system messages in update_chat_ctx for realtime models

[longcw]

preserves non-instruction system messages (e.g. context summaries) in update_chat_ctx for OpenAI realtime, instead of stripping all system messages.

fix #4875

[devin-ai-integration]

✅ Devin Review: No Issues Found

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[StianHanssen]

Thanks! Really appreciate the quick fix!

[chenghao-mou]

lgtm

[anmolgaud]

PR #4310 Also introduced exclude_instruction=true for google and aws realtime plugins also. The earlier verison of livekit didn't have any such restriction. They might also need to be fixed. We were previously using google-realtime models with the same approach.

Thanks a lot for this quick fix. A core feature of our agents was breaking because of this change.

[longcw]

@anmolgaud google realtime doesn't support system role, it only has user and model roles. before #4310 the system role was parsed as user message. and in the latest version, it will raise a warning that system message is going to be dropped, you may add your original system messages as user messages to keep the same behavior as before.