`auxiliary.<task>.provider: openai` was rewritten to custom + api.openai.com/v1 unconditionally, and the
api-key discovery rung used the registry default endpoint, so proxy/gateway users (OPENAI_BASE_URL or
providers.openai) had compression hop to the public endpoint with a proxy-issued key -> 401 -> the
key/pool was quarantined and the session sat over the compression threshold.
- _expand_direct_api_alias: a providers.openai entry keeps its name (named-custom branch applies its
base_url/key); otherwise OPENAI_BASE_URL wins over the public default.
- _resolve_api_key_provider: when the bound session runtime is that provider, use its endpoint + key.
- _recoverable_pool_provider: a rejection at a host other than the session's configured endpoint for
the same provider is an endpoint mismatch, not a dead key -> no rotation / unhealthy mark on the pool.
2db0c7a2d8