test(http): trace server socket ownership (GOL-420)

[noise64]

• extends GOL-420 transport diagnostics from guest/server body polling to the passive Axum socket boundary
• correlates each request with its accepted server connection and records socket read, write, error, shutdown, and drop outcomes without extra polls or awaits
• preserves pending response ownership with explicit overlap evidence instead of silently conflating pipelined requests
• validates real HTTP/1.1 pipelining through Axum ConnectInfo, Hyper body polling, and the wrapped AsyncWrite path
• keeps GOL-405 separate; this branch adds evidence only and does not retry, serialize, inflate timeouts, or change production transport behavior