fix(transport): close response body on 404 in sendHTTP (#849)

When sendHTTP receives a 404 (session terminated), it returns
(nil, ErrSessionTerminated) without closing resp.Body. All four
callers (SendRequest, SendNotification, createGETConnectionToServer,
sendResponseToServer) defer resp.Body.Close() only after checking
err == nil, so the body is never closed.

Under listenForever retry loops, each 404 leaks one TCP connection.
On long-running clients this eventually exhausts file descriptors.

Fix: close resp.Body before returning on the 404 path.

Author: blackwell-systems

client/transport/streamable_http.go

@@ -678,6 +678,7 @@ func (c *StreamableHTTP) sendHTTP(
 
 	// universal handling for session terminated
 	if resp.StatusCode == http.StatusNotFound {
+		resp.Body.Close()
 		c.sessionID.CompareAndSwap(sessionID, "")
 		return nil, ErrSessionTerminated
 	}