Function handle_frame 

pub async fn handle_frame(
    state: &AppState,
    access: &AccessContext,
    conn_id: &str,
    origin: Option<&str>,
    raw: &str,
    sink: &UnboundedSender<Value>,
)

Parse and dispatch a single inbound text frame. Any produced events are sent through sink. Returns Ok(()) always — protocol-level failures are surfaced as error events, never as hard errors that drop the connection.