Replace the OpenAI-compatible endpoint approach with the native
google-genai SDK for Vertex AI. This eliminates the custom token
refresher, TokenInjectingTransport, and async lifecycle complexity
while also removing the 8192 output token cap that the OpenAI
endpoint enforced.
Changes:
- vertexai provider now uses genai.Client(vertexai=True) instead of
AsyncOpenAI with token-injecting transport
- Routes through existing _call_gemini/_call_with_tools_gemini paths
- Strips google/ prefix from model names (native SDK uses bare names)
- Preserves service account key auth via credentials parameter
- Delete vertexai_token_refresher.py (no longer needed)
- Strip markdown code fences in consolidator JSON parsing
- Rewrite vertexai tests for native SDK integration