feat(pre-push-safety-net): preserve uncertainty in benchmark scoring

benchmarks/ranking/baselines/README.md

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+# Historical ranking measurements
+
+The eight JSON artifacts dated 2026-09-10 and 2026-09-11 are preserved as recorded.
+They predate the scoring correction in pre-push-safety-net task 1.3 and must not be
+interpreted as end-to-end detection or pre-push acceptance results.
+
+An audit on 2026-09-12 read all eight artifacts. Each records VAmPI-SQLI with
+`position: null`, `reached_transitively: true` and a repository `budget_at_recall`
+of 16. The old position instrument assigned that transitive label solely because
+it could not locate a matching region, then omitted the target from the budget
+calculation. These artifacts contain no queried witness establishing that label.
+This does not negate separately demonstrated VAmPI detections; it means this
+particular metric cannot establish them.
+
+Other recorded positions, scores, and elapsed stage costs remain historical
+observations under their recorded setup. Rank coverage is not detection recall,
+and a stage duration is not total hook latency. Use the corrected instrument and
+an explicit frozen profile for new comparisons. Retain unknown and unanswered
+cases, and require a queried target witness before counting transitive detection.
+Do not rewrite these files to make an earlier run appear to use the new semantics.