CVE-2026-86415: auto client cert connection reuse mixup

libcurl's connection-cache matcher never checks `auto_client_cert`, so a cached, already-authenticated Schannel connection can be handed to a transfer that just got redirected to a different origin, even though the code explicitly computed `auto_client_cert = FALSE` for that transfer to prevent …

// lib/vtls/vtls_config.c:236-238
sslc->auto_client_cert = Curl_peer_equal(origin, initial_origin) &&
                         !!(options & CURLSSLOPT_AUTO_CLIENT_CERT);