Kemal::Session::CookieOverflow

Raised by Session#save when the cookie would exceed Session::MAX_COOKIE_SIZE (the equivalent of Rails' ActionDispatch::Cookies::CookieOverflow). Browsers drop an oversized cookie silently, so without this the session would just vanish.

Because the cookie is written once per request by Session::Handler, this surfaces when the session is committed — as the response body starts — rather than from the setter that made the session too big.