v0.21.10

Fixes

• Google custom endpoints: skip Gemini Developer API model discovery before inference, so endpoint-scoped credentials reach the endpoint you configured. Previously any Google key triggered discovery against the hard-coded Developer API first, and a Vertex-scoped or proxied key failed there before your GOOGLE_BASE_URL was ever contacted. Discovery still runs when the endpoint is unset or explicitly the Developer API. Note that a custom endpoint now validates its own model IDs (#384, thanks @alfozan).