Response leak in SSE handlers

I found a resource leak in the streamable HTTP client. When SSE streaming fails with an exception, the HTTP response isn't closed.

Location:
src/mcp/client/streamable_http.py:

• _handle_sse_response (line 336)
• _handle_resumption_request (line 251)

The Issue:
python
async def _handle_sse_response(self, response: httpx.Response, ...):
try:
event_source = EventSource(response)
async for sse in event_source.aiter_sse():
if is_complete:
await response.aclose() # Only closed here
break
except Exception as e:
await ctx.read_stream_writer.send(e)
# response leaked!

If the SSE iteration raises an exception (malformed JSON, network error, etc.), the response is never closed.

Impact:
Connection pool gets exhausted in long-running clients, eventually causing new requests to hang or fail.

Fix:
try:
...
except Exception as e:
...
finally:
await response.aclose()

Both methods need this fix.

Env:
Python SDK version: 1.1.2 (or main branch)
Python: 3.12
Transport: StreamableHTTP

阅读 src/mcp/client/streamable_http.py，重点关注 _handle_sse_response 和 _handle_resumption_request。跟踪每个方法如何处理 SSE 迭代和异常，然后验证两条路径在失败后以及正常完成后都会关闭 HTTP 响应。