Replace the WinHTTP client with a ureq agent that keeps the same
Client/Response surface: status errors come back as responses, gzip,
60 s connect / 30 s receive / 120 s total timeouts, rustls with the
platform verifier and a per-request User-Agent override.
Environment proxies come from ureq. On Windows, when none is set, the
static Internet Settings proxy is read from HKCU and parsed by a pure
core module (per-scheme ProxyServer, ProxyOverride globs and <local>);
bypassed hosts go through a direct agent. PAC/WPAD is not evaluated.
The usage providers and credential sources compile again on every
platform. Refresh keeps the Windows candidates and CREATE_NO_WINDOW;
Unix spawns claude/codex from PATH plus the usual per-user install
directories and reaps the child on a detached thread. An empty
CODEX_HOME now counts as unset and a float expiresAt is truncated
instead of ignored.
Fixture tests cover the OAuth usage body, rate-limit headers (including
a 429 over loopback), the ChatGPT envelope, ISO 8601 edge cases,
credential JSON and proxy strings. An ignored live_poll test polls the
real providers.
