[Bugfix] Fix agnews query4 grading of incidental Africa mentions

[Jason-lang-ui]

The agnews/query4 validator accepts any answer containing Africa, including one that ranks North America first and Africa third. Require an affirmative first-place selection, allowing Africa to share first place.

Use a deterministic grammar for explicit answers, supported prose, numbered rankings and article-count tables. Cross-check winners, denials, ties, ranks and counts; fully parse numbers and table columns; preserve year/category/metric scope across blank lines and explicit answer transitions. Reject uncertain alternatives, retracted conclusions, malformed evidence and unsupported competing assertions. Unicode normalization and comparison-tail checks prevent conflicting claims from being silently dropped.

Validation: python3 -m unittest discover -s tests -v passes all 16 test methods, including the official controls over 104 validators and 1,658 answer-level regression cases. The matrices cover region substitutions, count ordering, ties, all three-column table permutations, malformed values, conflicting claims and heading scope. On the five observed answers, runs 0/1/3/4 pass and run 2 fails; run 0 retains its explicit first-place tie. The patch also applies cleanly to the upstream baseline and reproduces the tested files.

This is a bounded English grammar, not a complete semantic judge: correct unfamiliar wording can be rejected and may require manual review. The validate(str) -> (bool, str) interface is unchanged, with no new dependencies. If semantic judgment is required, it may be necessary to integrate LLM.