Add missing imports to test_integration.py

Added missing type annotation imports that were causing NameError and
preventing test collection:

- RequestResponder from mcp.shared.session
- SessionMessage from mcp.shared.message
- GetSessionIdCallback from mcp.client.streamable_http
- RequestContext from mcp.shared.context

This fixes 4 NameError collection failures and 10 F821 ruff errors,
allowing all 20 tests in the file to be properly collected and executed.

Author: felixweinberger

tests/server/fastmcp/test_integration.py

@@ -34,7 +34,10 @@
 )
 from mcp.client.session import ClientSession
 from mcp.client.sse import sse_client
-from mcp.client.streamable_http import streamable_http_client
+from mcp.client.streamable_http import GetSessionIdCallback, streamable_http_client
+from mcp.shared.context import RequestContext
+from mcp.shared.message import SessionMessage
+from mcp.shared.session import RequestResponder
 from mcp.types import (
     ClientResult,
     CreateMessageRequestParams,