Michael Freno
687df016a6
Every cold origin render of /changelog died with ERR_HTTP_HEADERS_SENT: the pending createAsync at the top of NookChangelogPage suspended the whole component before <EdgeCacheHeaders> rendered, the shell flushed while the S3 appcast fetch was in flight, and the boundary re-render then called setResponseHeader on an already-sent response. Warm renders hid it because the appcast's 5-minute module cache resolved in a microtask; fresh Vercel isolates and cache expiry hit the crash, which is why refreshes and direct navigation failed while in-app Links worked. deferStream holds the stream until the releases resolve, so HttpHeader always runs pre-flush. The S3 latency lands on origin renders only, which the page's CDN-Cache-Control s-maxage=300 already keeps rare. Tests: local prod-build cold-start loop (build + curl /nook/changelog), red 3/3 before, green 5/5 after; stack identical to the prod trace. Fixes FRE-112