NATIVE-ONLY http-request primitive (bin/sx_server.ml). HTTP/1.1 over
Unix sockets + gethostbyname; inline http:// URL parsing (full
url-parse deferred to Phase K); Connection: close + Host +
Content-Length headers auto-supplied; reads response via
Content-Length or read-to-EOF; chunked transfer-encoding rejected.
Test bin/test_http_client.sh spins a Phase-H echo server and drives
a second sx_server: GET+query, POST+body, 404, custom request
header reflected, non-http scheme rejected, integer status — 6/6.
WASM boot green (prim not in lib); Erlang conformance 530/530.
