fix(governance): improve artifact validation and error handling
- Move manual structural checks before jsonschema validation in
scripts/validate_gsifi_governance_assets.py to ensure error message
consistency with existing tests.
- Add comprehensive error handling for jsonschema exceptions during
validation.
- Ensure all tests in tests/test_validate_gsifi_governance_assets.py pass.
- Clean up __pycache__ directories.
Co-authored-by: OneFineStarstuff <87420139+OneFineStarstuff@users.noreply.github.com>