README: write_timeout in the Config sample, read/write timeout-split
semantics spelled out, new Streaming Responses and Server-Sent Events
sections (producer contract, 1.0 fallback, heartbeat liveness), roadmap
summary bumped. ROADMAP: v0.3 marked done with the as-landed decisions
(pull shape per the user's fork answer; Q3 timeout split as proposed)
and verified exit criteria. crud example: GET /ticker SSE route — one
event/second, producer exits on SseClosed or the example's shutdown
flag (so an open ticker doesn't block AllDone past the drain).