Tunables for CacheClientStore. Default carries the production values,
from_env applies operator overrides, and tests construct one directly
(short timeouts, near-zero or very long cooldown) instead of sleeping.
Why reading a streamed /ranges response body failed. Public API surface
(re-exported from lib.rs) so the cross-crate integration test can
assert on the exact failure kind directly (via send_ranges), rather than
inspecting logs or metrics.
Why send_ranges failed, keeping the header-phase failure, a non-2xx
status, and each RangesReadError body-failure kind distinct rather than
folding them into one. Public API surface (re-exported from lib.rs) for
the same reason as RangesReadError.