FIX: Fix multi-turn attacks using RealtimeTarget

[jsong468]

Description

This PR addresses the bug where executing multi-turn attacks against RealtimeTarget would not work properly because previous turn context was getting lost. The bug was caused by forced connection closes and reconnections to the OpenAI/AzureOpenAI server in send_text_async and send_audio_async, which caused all server-side conversation context to be lost.

• Removes the reconnection blocks from send_text_async and send_audio_async, and the WebSocket connection now persists across turns, preserving server-side conversation state
• Added guard on response.done event: skips the event if it's the very first event received (using current_turn_event_count tracking variable) and contains no audio. This occurs when an unconsumed response.done event is left in the WebSocket buffer from a prior turn's soft-finish when an audio.done event was received but no response.done after 1 second grace period. The method breaks normally if preceded by other events or if audio data is present
• Changed event type checks from if to elif since event types are mutually exclusive

Tests and Documentation

Added tests for multi-turn attacks with RealtimeTarget and re-ran notebook.

[romanlutz]

Did you check the GUI? Does it work there? It should, just asking.