When a configured Google provider/model row had no explicit
but had a baseUrl set, the fallback defaulted to openai-completions,
causing Gemini requests to route through the OpenAI Responses
transport instead of the native @google/genai transport.
Made resolveConfiguredProviderDefaultApi provider-aware: for the
google provider, the default API is now google-generative-ai.
Root cause: the generic fallback assumed any provider with a baseUrl
should use openai-completions, which is incorrect for Google's native
Gemini API.
Co-authored-by: xin <1052326311+xin@users.noreply.github.com>
b73e135f97