Mark whether the negotiated protocol version is modern (2026-07-28 / draft). When true, postAndAwait skips Last-Event-ID resumption via GET because the draft removed SSE resumability; a draft server responds to such a GET with 405.
Mark whether the negotiated protocol version is modern (2026-07-28 / draft). When true, postAndAwait skips Last-Event-ID resumption via GET because the draft removed SSE resumability; a draft server responds to such a GET with 405.