Minimal async HTTP/1.1 client for the Moirai runtime.
Runs over Moirai async sockets and [moirai_tls] — no Tokio. Scope is the
request shapes object-storage clients need (GET with Range, HEAD, small
PUT/POST bodies): Content-Length and chunked response framing, a bounded
keep-alive connection pool, and per-request timeouts. HTTP/2 is out of scope
(ADR-015). Vendor protocols (e.g. S3 SigV4) are built by callers on top of this
— this crate knows HTTP, not S3.