Document RAY_ENABLE_UV_RUN_RUNTIME_ENV flag

Co-authored-by: Kevin Liu <kevinjqliu@users.noreply.github.com>

Author: afeldman1

tests/conftest.py

@@ -3030,6 +3030,11 @@ def pyarrow_table_with_promoted_types(pyarrow_schema_with_promoted_types: "pa.Sc
 
 
 def pytest_configure(config: pytest.Config) -> None:
+    # Disable Ray's automatic uv environment propagation to workers.
+    # When tests are invoked via `uv run`, Ray detects the wrapper and tries
+    # to package the working directory for remote workers, which is unnecessary
+    # and problematic in local single-node test mode
+    # See https://docs.ray.io/en/latest/_modules/ray/_private/worker.html
     os.environ["RAY_ENABLE_UV_RUN_RUNTIME_ENV"] = "0"