Fix Python cookbook recipes to use correct async SDK API

All 5 Python recipes and their markdown docs used a synchronous,
kwargs-based API that doesn't match the real github-copilot-sdk:

- client.start() -> await client.start() (all methods are async)
- create_session(model=...) -> create_session(SessionConfig(model=...))
- session.send(prompt=...) -> session.send(MessageOptions(prompt=...))
- session.wait_for_idle() -> session.send_and_wait() (wait_for_idle doesn't exist)
- event['type']/event['data']['content'] -> event.type/event.data.content
- All code wrapped in async def main() + asyncio.run(main())

Verified all imports resolve against github-copilot-sdk.

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

@@ -1,28 +1,25 @@
 #!/usr/bin/env python3
 
-from copilot import CopilotClient
+import asyncio
+from copilot import CopilotClient, SessionConfig, MessageOptions
 
-client = CopilotClient()
+async def main():
+    client = CopilotClient()
 
-try:
-    client.start()
-    session = client.create_session(model="gpt-5")
+    try:
+        await client.start()
+        session = await client.create_session(SessionConfig(model="gpt-5"))
 
-    response = None
-    def handle_message(event):
-        nonlocal response
-        if event["type"] == "assistant.message":
-            response = event["data"]["content"]
+        response = await session.send_and_wait(MessageOptions(prompt="Hello!"))
 
-    session.on(handle_message)
-    session.send(prompt="Hello!")
-    session.wait_for_idle()
+        if response:
+            print(response.data.content)
 
-    if response:
-        print(response)
+        await session.destroy()
+    except Exception as e:
+        print(f"Error: {e}")
+    finally:
+        await client.stop()
 
-    session.destroy()
-except Exception as e:
-    print(f"Error: {e}")
-finally:
-    client.stop()
+if __name__ == "__main__":
+    asyncio.run(main())