google-cloud-aiplatform>=1.142.0 fails to import vertexai.types with google-genai<1.66.0 due to missing BigQuerySource #6536

Summary

Since v1.142.0, vertexai._genai.types.common references google.genai.types.BigQuerySource, but the declared dependency lower bound is google-genai>=1.59.0. BigQuerySource was only added in google-genai==1.66.0, so any resolution in the range [1.59.0, 1.66.0) fails at runtime.

Steps to reproduce

1. uv init --bare
2. uv add 'google-cloud-aiplatform==1.142.0' 'google-genai==1.65.0' - same for the latest 1.144.0
3. uv run python -c "import importlib; importlib.import_module('vertexai._genai.types')"

Expected: no error
Actual:

`AttributeError: module 'google.genai.types' has no attribute 'BigQuerySource'`

The normal user-facing import from vertexai import types surfaces this as

ImportError: cannot import name 'types' from 'vertexai'

Using google-genai==1.66.0 fixes it:

uv add 'google-genai==1.66.0'
uv run python -c "from vertexai import types; print('OK')"
# OK

I suspect that 3cd949d requires bumping lower bound of google-genai.