test(py): add unit tests for wrap_gemini wrapper function

[saikiranAnnam]

Closes #2818

Problem

wrap_gemini was introduced in langsmith 0.4.33 but didn’t have direct unit tests covering the public wrapper, only the internal processing helpers (_process_gemini_inputs, _create_usage_metadata, etc.) were tested.

This meant the public import path and wrapping behavior weren’t protected against regressions.

Changes

Adds python/tests/unit_tests/wrappers/test_wrap_gemini.py with 9 unit tests:

Test	What it guards
test_importable_from_langsmith_wrappers	langsmith.wrappers.wrap_gemini is accessible (the exact AttributeError from #2818)
test_importable_directly	from langsmith.wrappers import wrap_gemini works
test_in_wrappers_all	wrap_gemini stays in __all__ across refactors
test_wraps_sync_generate_content	models.generate_content is replaced and __wrapped__ is set
test_wraps_sync_generate_content_stream	Same for the streaming method
test_wraps_async_generate_content	aio.models.generate_content is replaced and __wrapped__ is set
test_double_wrap_raises	ValueError is raised on a second wrap_gemini call
test_partial_client_does_not_crash	Clients missing aio or stream methods don't raise
test_beta_warning_emitted	LangSmithBetaWarning is emitted (beta API contract)

No source changes — tests only. Mock clients require no google-genai package installed.

This adds regression protection for the public API surface.

Testing

cd python
make format
make lint
make tests