End-to-end test of the server->client request round-trip between this SDK's
own McpServer and McpClient, over a real Streamable HTTP transport.
A tool that calls ctx.sample/ctx.elicit emits a server->client request on
its POST's SSE stream and blocks in StreamCoordinator.await; the client must
answer it on a separate POST while its own fiber is still reading that SSE
stream. With vibe.d's keep-alive connection pool, the reply POST must not block
waiting for the in-flight request's connection to be released.
End-to-end test of the server->client request round-trip between this SDK's own McpServer and McpClient, over a real Streamable HTTP transport.
A tool that calls ctx.sample/ctx.elicit emits a server->client request on its POST's SSE stream and blocks in StreamCoordinator.await; the client must answer it on a separate POST while its own fiber is still reading that SSE stream. With vibe.d's keep-alive connection pool, the reply POST must not block waiting for the in-flight request's connection to be released.