Pure Server-Sent Events wire encoding for the realtime events endpoint.

Frames map a Postgres NOTIFY onto SSE's native fields: the channel name is the event: field and the payload is carried verbatim in data: lines — no envelope is invented. A payload containing line breaks (\n, \r\n, or a bare \r — all line terminators to an SSE parser) is split across consecutive data: lines, which clients reassemble joined with \n; a raw CR left inside a data: line would instead be treated as a line break by the client's parser, silently truncating the payload after it.