Prevent update_chat_ctx from deleting in-flight function calls using function call attributes

[StianHanssen]

Summary

update_chat_ctx can delete in-flight function_call items from the OpenAI Realtime server, causing cascading "failed to insert item: previous_item_id not found" corruption of _remote_chat_ctx.

The root cause is a timing gap between two context-tracking structures:

• _remote_chat_ctx: Updated immediately when the server sends conversation.item.added
• _agent._chat_ctx: Updated later, only when tool execution starts (_tool_execution_started_cb)

If update_chat_ctx runs during this window (e.g. from context management), the diff sees the function_call in remote but not in local, treats it as intentionally removed, and sends a delete event. The existing _is_content_empty guard only protects message items — function_call items pass through unconditionally.

A unit test gist replicating the exact pipeline demonstrates how update_chat_ctx deletes in-flight function_call items.

Fix

Use a shared-object flag (extra["dispatched"]) on FunctionCall items to distinguish in-flight from intentionally removed function calls.

1. openai_item_to_livekit_item sets extra["dispatched"] = False when creating a FunctionCall from a server event.

2. _handle_function_call reuses the same FunctionCall object from _remote_chat_ctx instead of creating a new one. This is safe because conversation.item.added always precedes response.output_item.done on the websocket. The same Python object is now shared across both contexts.

3. _create_update_chat_ctx_events skips deletion for any function_call with extra["dispatched"] == False. Once the flag is True, summarization and other callers can delete the item normally.

4. agent_activity.py sets extra["dispatched"] = True when tool execution starts or when all function calls for a generation are finalized (after await exe_task). Since the object is shared, this is visible to the diff guard immediately — no cross-package signaling needed.

Future consideration

This fix only tracks function_call items. function_call_output items are currently client-initiated (manual_function_calls=True), so they enter _agent._chat_ctx before _remote_chat_ctx and are not vulnerable to this race. If auto_tool_reply_generation is enabled in a future configuration (server-generated outputs), a guard should be added to cover function_call_output items as well.