Write an already-serialized JSON-RPC line as a single newline-delimited line,
serialized against concurrent writers. Used by callers that already hold the
serialized text (the stdio server sink and reply path) so the line is not
parsed back to Json only to be re-serialized. The caller is responsible for
the text being one valid MCP message with no embedded newline.
Write an already-serialized JSON-RPC line as a single newline-delimited line, serialized against concurrent writers. Used by callers that already hold the serialized text (the stdio server sink and reply path) so the line is not parsed back to Json only to be re-serialized. The caller is responsible for the text being one valid MCP message with no embedded newline.