.NET & Python: Support THINKING_TEXT_MESSAGE Events in AgentFrameworkEventBridge #2619

# agent_framework_ag_ui/_events.py (current implementation)
def from_agent_run_update(update: AgentRunResponseUpdate):
    for content in update.contents:
        if isinstance(content, TextContent):
            yield TEXT_MESSAGE_CONTENT event
        elif isinstance(content, FunctionCallContent):
            yield TOOL_CALL_* events
        elif isinstance(content, FunctionResultContent):
            yield TOOL_RESULT_* events
        # ❌ TextReasoningContent is not handled - content is lost

# Proposed change to agent_framework_ag_ui/_events.py
from ag_ui.core.events import (
    ThinkingStartEvent,
    ThinkingTextMessageStartEvent,
    ThinkingTextMessageContentEvent,
    ThinkingTextMessageEndEvent,
    ThinkingEndEvent,
)
from agent_framework import TextReasoningContent

def from_agent_run_update(update: AgentRunResponseUpdate):
    # Track thinking state
    thinking_active = False
    
    for content in update.contents:
        if isinstance(content, TextContent):
            # Existing text handling
            yield TEXT_MESSAGE_CONTENT event
            
        elif isinstance(content, TextReasoningContent):
            # NEW: Handle reasoning content
            if not thinking_active:
                yield ThinkingStartEvent()
                yield ThinkingTextMessageStartEvent()
                thinking_active = True
            
            # Check if this is a delta or done event
            raw = content.raw_representation
            event_type = getattr(raw, 'type', '') if raw else ''
            
            if 'delta' in event_type:
                # Stream incremental content
                yield ThinkingTextMessageContentEvent(
                    delta=content.text
                )
            elif 'done' in event_type:
                # End of reasoning section
                yield ThinkingTextMessageEndEvent()
                yield ThinkingEndEvent()
                thinking_active = False
                
        elif isinstance(content, FunctionCallContent):
            # Existing tool call handling
            yield TOOL_CALL_* events

# Backend: Azure OpenAI with reasoning enabled
agent = responses_client.create_agent(
    additional_chat_options={
        "reasoning": {"summary": "detailed"}
    }
)

# Frontend: AG-UI automatically receives thinking events
subscriber.on('THINKING_TEXT_MESSAGE_CONTENT', (event) => {
    displayThinkingProcess(event.delta);
});