Add 6 new tests using sample-listing-empty.html and
sample-listing-call.html fixtures:
- Verify empty section container returns empty array
- Verify zero-count logging for empty fixtures
- Verify extraction of "Call for pricing" units
- Verify raw string preservation for price fields
- Verify all attribute extraction from call-for-pricing units
- Verify image_url handling when img elements are absent
Total parseUnits test coverage: 28 tests across 9 describe blocks.
