//! Authentication handshake logic.
//!
//! The auth flow is handled inline during transport connection:
//!
//! - **WebSocket** (`connection::connect_ws`): Sends `SystemOp::Auth` as the
//! first text message, waits for `SystemOp::AuthOk` response.
//! - **SSE** (`connection::connect_sse`): Auth params are passed as URL query
//! parameters; `AuthOk` arrives as the first SSE event.
//!
//! Resume is supported by including `resume_cursors` in the auth message.
//! The server replays any buffered frames from the requested cursor positions.