Aligns with the parallel hardening from draft PR #13848 (now closed as
a duplicate). The validator now:
- Raises ValueError on non-string list items (was: silently dropped).
- Raises ValueError on non-string / non-list top-level values like dict
or int (was: silently passed through to Pydantic's downstream coercion).
Adds tests-unit/assets_test/queries/test_list_assets_query.py covering
the validator end-to-end: CSV canonicalization, dedup order, default
empty, invalid UUID, non-string list item, non-string non-list value,
and the max_length=500 boundary.
a3f2359a18