Gate findings folded: the accepted path is derived from the provider's
catalog default (/anthropic for MiniMax, /plan/anthropic for Tencent) instead
of a hardcoded /anthropic prefix, so /anthropic-compat no longer passes and a
non-/anthropic default provider's own endpoint does; an empty base_url keeps
the declared transport like an unknown default; the catalog read is
allow_network=False (determine_api_mode just warmed it); _base_url_path is
shared with URL detection. Tests pin the catalog defaults they compare
against so the contract holds offline.
dbdcb83d77