test(cypher): regression guards for #240/#237/#252/#305 (already supported)

Confirmed working in the current query_graph evaluator and locked in:
- #240 labels() function with AS alias
- #237 DISTINCT applied before ORDER BY + LIMIT
- #252 toInteger()
- #305 count(*) with AS alias

Closes #240. Closes #237. Closes #252. Closes #305.