nx_rank_fused_test.nx

nx_rank_fused_test.nx -- KAT for the additive tier+BM25+RRF ranker. Native sovereign lane; exit 0 = pass, N = assertion N failed. The thesis, proven end-to-end on a controlled 5-doc corpus, query "diora": A(0): high tier (IMDb primary) + relevant content -> best in BOTH B(1): high tier (IMDb primary) + NO relevant content -> authority only C(2): low tier (unknown blog) + STRONG relevant content D(3): platform, no content; E(4): unknown, no content Expected: A ranks #1 (best in both); and C (low-tier but relevant) ranks ABOVE B (high-tier but irrelevant) -- content beats domain prejudice.