HTTP client
A single *http.Client on the Factory, built from a composable
http.RoundTripper middleware chain; deterministic httptest seams
in tests.
Decisions
byob-http-client.1— net/http + RoundTripper middleware chain, not retryablehttp/restybyob-http-client.2— HTTPClient on the Factory as a lazy closure with tuned timeoutsbyob-http-client.3— Retry policy: bounded exponential + jitter, idempotent-by-default, Retry-After awarebyob-http-client.4— Test HTTP via httptest.NewServer, not gock/httpmockbyob-http-client.5— User-Agent: <tool>/<version> (<os>; <arch>)