[findings] PR 1+2 で計測完了。1177 events / 218 posts:

- db:instantiate 5.0s
- fetch 0.14s
- apply 13.9s(per-event×2 query = 2354 worker round-trips)
- total 14.2s
- fetchAll 19.5s

支配:apply の per-event DuckDB-WASM 往復。X 路線(server projection 配信)が landed すれば消える層。