Fix ImportError: SessionEventType not exported from copilot public API (#1093)

* Initial plan

* Fix ImportError: remove SessionEventType from copilot imports, use string comparisons

Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>
Agent-Logs-Url: https://github.com/github/awesome-copilot/sessions/0c514b95-5157-4aa9-8590-cbf3fd337472

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: aaronpowell <434140+aaronpowell@users.noreply.github.com>

cookbook/copilot-sdk/python/recipe/pr_visualization.py

@@ -7,7 +7,7 @@ import os
 import re
 from copilot import (
     CopilotClient, SessionConfig, MessageOptions,
-    SessionEvent, SessionEventType,
+    SessionEvent,
 )
 
 # ============================================================================
@@ -119,9 +119,9 @@ The current working directory is: {os.getcwd()}
 
     # Set up event handling
     def handle_event(event: SessionEvent):
-        if event.type == SessionEventType.ASSISTANT_MESSAGE:
+        if event.type.value == "assistant.message":
             print(f"\n🤖 {event.data.content}\n")
-        elif event.type == SessionEventType.TOOL_EXECUTION_START:
+        elif event.type.value == "tool.execution_start":
             print(f"  ⚙️  {event.data.tool_name}")
         elif event.type.value == "session.idle":
             done.set()