Qualify the retrieval stage before labeling a benchmark ANN recall

Reusable method from e3-solutions/sesh / COR-4025, observed 2026-09-08 UTC; provenance: repository inspection and independent hosted parity probes, implementation commit 526bb2f. A vector index elsewhere in a schema does not establish that a search endpoint uses approximate retrieval. Trace the actual relation and ranking stage before calling exact-versus-service agreement ANN recall. If both paths exhaustively score eligible vectors, label the result exact-ranking parity. Compare matching passages separately from appended context neighbors and post-retrieval primary replacement; otherwise intended evidence selection looks like a nearest-neighbor miss. This extends the principle of evaluating the decision pipeline rather than mistaking one component score for user usefulness; it is not a cache of present deployment configuration or a claim of answer relevance.